Neighborhood node mapping methods and apparatus for ingress mitigation in cable communication systems

ABSTRACT

A mobile transmitter traverses a drive path in a neighborhood node of a cable communication system and broadcasts a test signal at frequencies falling within an upstream path bandwidth. A navigational device generates a first record of positions of the transmitter along the drive path, and an analyzer monitors the upstream path bandwidth and generates a second record of received signal amplitudes of the transmitted test signal as a function of time. An ingress map is generated showing the drive path and potential points of ingress in the node, and employed to remediate faults particularly in the hardline coaxial cable plant. Iterative generation of maps and corresponding remediation in the node enable improved cable communication systems with reduced noise profiles between 5 MHz and 20 MHz and employing higher modulation order QAM communication channels (e.g., 256-QAM and higher) throughout the upstream path bandwidth to increase upstream capacity.

CROSS-REFERENCES TO RELATED APPLICATIONS

The present application claims a priority benefit, under 35 U.S.C.§119(e), to the following U.S. provisional applications:

Ser. No. 61/503,906, filed Jul. 1, 2011, entitled “METHODS, APPARATUSAND SYSTEMS FOR INGRESS DETECTION AND REMEDIATION;”

Ser. No. 61/538,646, filed Sep. 23, 2011, entitled “METHODS, APPARATUSAND SYSTEMS FOR INGRESS DETECTION AND REMEDIATION;” and

Ser. No. 61/544,895, filed Oct. 7, 2011, entitled “METHODS, APPARATUSAND SYSTEMS FOR INGRESS DETECTION AND REMEDIATION.”

Each of the above-identified applications is hereby incorporated hereinby reference in its entirety.

BACKGROUND

Cable communication systems provide one or more of commercial TVservices, Internet data services, and voice services (e.g.,“Voice-over-Internet Protocol,” or VoIP) to one or more subscriberpremises (or “end users”) in a given geographic area. Generallyspeaking, a cable communication system refers to the operational (e.g.,geographical) footprint of an entertainment and/or information servicesfranchise that provides entertainment and/or information services to asubscriber base spanning one or more towns, a metropolitan area, or aportion thereof. Particular entertainment and/or information servicesoffered by the franchise (e.g., entertainment channel lineup, datapackages, etc.) may differ from system to system. Some large cablecompanies operate several cable communication systems (e.g., in somecases up to hundreds of systems), and are known generally as MultipleSystem Operators (MSOs).

Cable Communication System Overview

FIG. 1 generally illustrates various elements of a conventional hybridfiber-coaxial (HFC) cable communication system 160. The cablecommunication system 160 includes a headend 162 coupled to one or morenodes 164A, 164B and 164C via one or more physical communication media.The physical communication media typically include fiber optic cable andcoaxial cable to convey information (e.g., television programming,Internet data, voice services) between the headend 162 and subscriberpremises served by the nodes 164A, 164B and 164C of the cablecommunication system 160.

In FIG. 1, a first node 164A is illustrated with some detail to showmultiple subscriber premises 190 as well as additional elements thatsimilarly may be found in the other nodes 164B and 164C. In general, theheadend 162 transmits information to and receives information from agiven node via physical communication media (i.e., fiber optic cable andcoaxial cable) dedicated to serving the geographic area covered by thenode. Although the physical communication media of a given node may passproximate to several premises, not all premises passed are necessarilysubscriber premises 190 (i.e., actual subscribers to the servicesprovided by the cable communication system 160); in some conventionalcable communication systems, subscriber premises 190 of a given node mayconstitute on the order of 50% of the total number of premises passed bythe physical communication media serving the node.

Although FIG. 1 illustrates only three subscriber premises 190 in thefirst node 164A, it should be appreciated that the geographic areacovered by a representative node of a conventional cable communicationsystem typically includes anywhere from approximately 100 premises to asmany as 1000 premises (not all of which may be subscriber premises 190).Also, while FIG. 1 shows only three nodes 164A, 164B and 164C coupled tothe headend 162, it should be appreciated that cable communicationsystems similar to the system 160 shown in FIG. 1 may include differentnumbers of nodes (e.g., for some larger cable communication systems, theheadend may serve several hundreds of nodes).

Nodes

The first node 164A shown in FIG. 1 is depicted generally as either a“Fiber to the Neighborhood” (FTTN) node (also sometimes referred to as a“Fiber to the Feeder” or FTTF node), or a “Fiber to the Curb” (FTTC)node. In an FTTN/FTTF or FTTC node, fiber optic cable is employed as thephysical communication medium to communicate information between theheadend 162 and the general geographic area of subscriber premises.Within the area occupied by the subscriber premises, coaxial cable isemployed as the physical communication medium between the fiber opticcable and respective subscriber premises 190. A general differencebetween FTTN/FTTF and FTTC nodes relates to how close the fiber opticcable comes to the premises in the node, and how many premises arepassed by the coaxial cable portion of the node; for example, in an FTTCnode, the fiber optic cable generally comes closer to the premises inthe node than in an FTTN/FTTF node, and the coaxial cable portion of theFTTC node typically passes fewer than 150 premises (whereas the coaxialcable portion of an FTTN/FTTF node passes as many as from 200 to 1000premises, as discussed further below). Unlike cable communicationsystems employing FTTN/FTTF and FTTC nodes, “Fiber to the Home” (FTTH)systems (also knows as “Fiber to the Premises” or FTTP systems) have aprimarily fiber optic cable infrastructure (a “passive optical network”or PON) that runs directly and respectively to some smaller number ofsubscriber premises (e.g., approximately 30 or fewer premises passed).

As shown in FIG. 1, the first node 164A has an infrastructure (alsoreferred to generally herein as a “cable plant”) that includes a firstfiber optic cable 163A, a first optical/radio frequency (RF) converter167, a first RF hardline coaxial cable plant 180, a plurality of firstsubscriber service drops 163C, and a plurality of first subscriberpremises 190.

More specifically, the first node 164A includes a first fiber opticcable 163A, coupled to the headend 162 of the cable communication system160 and to a first optical/radio frequency (RF) converter 167 (alsosometimes referred to as a “bridge converter”) within the first node164A. As noted above, depending on the configuration of the node as anFTTN/FTTF node or an FTTC node, the first optical/RF bridge converter167 may be physically disposed at various geographic locations coveredby the first node 164A. The bridge converter 167 generally serves toconvert optical signals transmitted by the headend 162 to radiofrequency (RF) signals that are received by subscriber premises 190 inthe first node; the bridge converter 167 also converts RF signalstransmitted by the subscriber premises 190 to optical signals that arereceived at the headend 162.

The first node 164A also includes a first RF hardline coaxial cableplant 180 (also referred to herein simply as a “hardline cable plant”)coupled to the bridge converter 167. The first hardline cable plant 180constitutes another portion of the physical communication media overwhich information is carried, in the form of RF signals (e.g., modulatedRF carrier waves), between the optical/RF bridge converter 167 and thesubscriber premises 190 of the first node. Additional details of thefirst hardline cable plant 180 are discussed below in connection withFIG. 2.

As shown in FIG. 1, the first node 164A further includes multiple firstsubscriber service drops 163C, coupled to the first hardline cable plant180 and respectively associated with subscriber premises 190. Each ofthe subscriber premises 190 includes one or more end-user modems 165(also referred to herein as “subscriber modems” or “media terminaladapters”) to demodulate RF signals carrying data and/or voiceinformation and received from the first hardline plant 180 via thepremises' corresponding subscriber service drop 163C (a differentdevice, commonly known as a “set-top box,” is typically employed at asubscriber premises to demodulate RF signals carrying videoinformation). The subscriber modem(s) 165 also modulate an RF carrierwith information (e.g., data and/or voice information) to be transmittedfrom the subscriber premises 190 to the first hardline cable plant 180.Thus, the first subscriber service drops 163C communicatively couple thesubscriber modem(s) 165 of the respective subscriber premises 190 to thefirst hardline cable plant 180.

In the cable communication system 160 of FIG. 1, the first cablehardline plant 180 (as well as the first subscriber service drops 163C)carries RF signals that convey downstream information 183 from theheadend 162 (as received via the fiber optic cable 163A and the bridgeconverter 167) to the subscriber premises 190 of the first node 164A.The first hardline cable plant also carries RF signals that conveyupstream information 184 from at least some of the subscriber premises190 of the first node 164A to the bridge converter 167 (which upstreaminformation ultimately is transmitted to the headend 162 via the fiberoptic cable 163A). To this end, the RF communication bandwidth supportedby the first hardline cable plant 180 typically is divided into adownstream path bandwidth 181 in which the downstream information 183 isconveyed, and an upstream path bandwidth 182 in which the upstreaminformation 184 is conveyed. In most conventional cable communicationsystems in the United States, the upstream path bandwidth 182 includes afirst frequency range of from 5 MHz to 42 MHz (in other geographies, theupstream path bandwidth may extend to a higher frequency; for example,in Europe the upstream path bandwidth includes frequencies from 5 MHz to65 MHz). The downstream path bandwidth 181 includes a second frequencyrange of from 50 MHz to 750 MHz (and in some instances as high asapproximately 1 GHz). The downstream information 183 is conveyed by oneor more downstream RF signals having a carrier frequency falling withinthe downstream path bandwidth 181, and the upstream information 184 isconveyed by one or more upstream RF signals having a carrier frequencyfalling within the upstream path bandwidth 182.

As noted above, the nodes 164B and 164C typically cover differentgeographic areas within the overall operating footprint of the cablecommunication system 160, but may be configured similarly to the firstnode 164A with respect to the various infrastructure constituting thenode (e.g., each of the nodes 164B and 164C may include a dedicatedfiber optic cable, optical/RF bridge converter, hardline plant,subscriber premises, and subscriber service drops to subscriberpremises).

As also noted above, the overall infrastructure of a given node isreferred to generally herein as a “cable plant,” with respectiveconstituent elements of the cable plant including the first fiber opticcable 163A, the first optical/radio frequency (RF) converter 167, thefirst RF hardline coaxial cable plant 180, the plurality of firstsubscriber service drops 163C, and the plurality of first subscriberpremises 190, as illustrated in FIG. 1. These respective elements havecorresponding roles and functions within the cable plant (and the cablecommunication system as a whole); accordingly, it should be appreciatedthat while “cable plant” may refer to any one or more nodeinfrastructure elements in combination, specific elements of the cableplant are referred to with particularity when describing theircorresponding roles and functions in the context of the inventiveconcepts discussed in subsequent sections of this disclosure. Forexample, “RF hardline coaxial cable plant” (or “hardline cable plant”)refers specifically to the element 180 as introduced above in connectionwith FIG. 1, described further below in connection with FIG. 2, andsimilarly implemented according to various embodiments of inventiveconcepts discussed in subsequent sections of this disclosure.

In particular, FIG. 2 illustrates additional details of the firsthardline cable plant 180 of the first node 164A. FIG. 2 also shows thefirst optical/RF converter 167 of the first node (to which the firsthardline cable plant 180 is coupled), as well as one subscriber premises190 of the first node (coupled to the first hardline cable plant 180 viaa subscriber service drop 163C). Although only one subscriber premises190 is shown in FIG. 2 for purposes of illustration, it should beappreciated that multiple subscriber premises may be coupled to thehardline cable plant 180 (e.g., as shown in FIG. 1). In FIG. 2, thefirst hardline cable plant 180 is indicated generally with dashed linesso as to distinguish various elements of the hardline cable plant 180from the optical/RF converter 167 and other elements of the cablecommunication system generally associated with one or more subscriberpremises 190. As noted above, hardline cable plants employed in othernodes of the communication system 160 shown in FIG. 1 generally mayinclude one or more of the various elements shown in FIG. 2 asconstituting the first hardline cable plant 180, and may be similarlyconfigured to the first hardline cable plant 180.

As conventional cable communication systems have evolved over the years,so has some nomenclature for various elements of the system and,particularly, the hardline cable plant. Turning again to FIG. 2, a firstsegment of the hardline coaxial cable 163B in the hardline cable plant180, between the optical/RF bridge converter 167 and a first amplifier187 (e.g., in which power supply 186 is connected via connector 193), issometimes referred to as an “express feeder” (historically, an expressfeeder was sometimes considered/referred to as part of the “trunk”). Anexpress feeder may run for various distances and generally does notinclude any distribution taps 188. Conversely, a section of the hardlinecable plant including one or more segments of hardline coaxial cable163B and one or more distribution taps 188 sometimes is referred tomerely as a “feeder” (as opposed to an “express feeder”). It should beappreciated that the terminology “trunk,” “express feeder,” and “feeder”are merely referred to above as examples of nomenclature used in theindustry for various portions of the cable communication system andhardline cable plant. In exemplary implementations, various elements ofthe hardline cable plant 180 often are disposed above the ground, e.g.,mounted on and/or hung between utility poles, and in some cases elementsof the hardline cable plant also or alternatively may be buriedunderground.

As shown in FIG. 2, the first hardline cable plant 180 includes one ormore segments of hardline coaxial cable 163B (one of which segments iscoupled to the optical/RF converter 167). The hardline cable plant 180also may include one or more components generally categorized as an“active” component, a “passive” component, a power supply, a connector,or various hardware (e.g., clamps, hangers, anchors, lashing wire, etc.)employed to secure various components to each other or other supportinginfrastructure (e.g., utility poles, underground conduit, etc.). Morespecifically, with reference to FIG. 2, the hardline cable plant mayinclude: one or more amplifiers 187 (also sometimes referred to as “lineextenders”) constituting an active component and requiring power fromone or more power supplies 186; one or more passive components, examplesof which include distribution taps 188 (also referred to simply as“taps”), directional couplers 189 (also referred to as “splitters” or“combiners”), line terminators 191, and filters/attenuators (not shownexplicitly in FIG. 2, although a filter/attenuator may be a constituentcomponent of a tap, splitter/combiner, or a line terminator); one ormore connectors or “fittings” 193 for coupling segments of the hardlinecoaxial cable 163B to various other elements of the hardline cable plant180 (e.g., pin-type connectors, such as housing terminators, extensionfittings, 90-degree fittings, splice connectors, etc., or one or more“splice blocks” 195 that may be employed to interconnect two segments ofhardline coaxial cable 163B). FIGS. 3A through 3G illustrates examplesof these various elements, which are discussed in greater detail in turnbelow.

With respect to the hardline coaxial cable 163B used in the hardlinecable plant 180, as shown in FIG. 3A the coaxial cable commonly employedin the hardline plant often includes a center solid conductor surroundedby an electrically insulating material and a solid conductor shield toprovide for improved electrical characteristics (e.g., lower RF signalloss/leakage) and/or some degree of environmental robustness. Some typesof coaxial cables used for the hardline plant 180 include low densityfoam (LDF) insulation, which has insulating qualities similar to dryair, making it particularly well-suited for outdoor use. The solidconductor shield generally makes the cable somewhat more difficult tobend (hence the terminology “hardline” coaxial cable). In variousimplementations, 0.75 inch hardline coaxial cable may be employed for“express feeders,” whereas 0.625 inch hardline coaxial cable may beemployed for “feeders.” One example of hardline coaxial cable 163Bconventionally employed in the hardline plant 180 is given CommscopePIII 0.625 cable (e.g., seehttp://www.commscope.com/broadband/eng/product/cable/coaxial/1175378_(—)7804.html).However, it should be appreciated that a variety of hardline coaxialcables may be employed in different hardline plants and/or differentportions of the same hardline plant. Additionally, hardline tri-axialcable also is available that includes an additional shield layer todiscourage electromagnetic interference, and may in some instances beemployed in a hardline plant (for purposes of the present disclosure,any reference to “hardline coaxial cable” should be understood toinclude hardline tri-axial cable as well).

With reference again to FIG. 2, as noted above the hardline cable plant180 also may include one or more power supplies 186 and one or moreamplifiers 187 or “line extenders” (also shown in FIG. 3F). An exemplarypower supply 186 converts commercially-available power (e.g., 120 VoltsA.C. rms, 60 Hz) to voltage amplitudes (e.g., 60 VAC, 90 VAC) that maybe distributed (e.g., in some cases along with RF signals via thehardline coaxial cable 163B) for providing power to one or moreamplifiers 187 or other active components of the hardline cable plant.One or more amplifiers 187 may be employed to boost attenuated RFsignals for further propagation or distribution along the hardline cableplant 180 (in one or both of the upstream path bandwidth or thedownstream path bandwidth). Some types of amplifiers 187 may bebi-directional and provide separate amplification pathways fordownstream and upstream RF signals, respectively. It should beappreciated that for purposes of the present discussion, the term“amplifier” is used generally to refer to a device that may amplify asignal; in some examples, an amplifier also may implement a filteringfunction as well (e.g., selective attenuation/amplification at one ormore particular frequencies or over one or more frequency bands) for oneor more RF signals propagating along the hardline cable plant 180. Inparticular, hardline cable plant amplifiers 187 typically include“diplex filters” that allow passage of signals through the amplifieronly in the frequency ranges prescribed for the upstream path bandwidthand the downstream path bandwidth, respectively.

In conventional implementations of hardline coaxial cable plants,amplifiers may be distributed along the hardline coaxial cable plant ofa given node at distances of approximately 1200 feet between amplifiers.One typical characterization of a node is referred to as “cascade,”which refers to the number of amplifiers in the longest branch of thehardline coaxial cable plant in the node. More specifically, the cascadefor a given node often is denoted as “NODE+N,” in which N denotes thenumber of amplifiers between the RF/optical bridge converter of the nodeand an endpoint of the longest branch of the hardline coaxial cableplant in the node. With reference to FIG. 2, the illustrated example ofthe hardline cable plant 180 includes two amplifiers 167; if thisillustration represented the entire hardline cable plant in the firstnode 164A, the cascade for this node would be referred to as “NODE+2.”In many conventional implementations of cable communication systems,typical cascades for hardline coaxial cable plants in respective nodesof the system are five or six (i.e., NODE+5 and NODE+6) (see section3.1, pages 3-4 of “Architecting the DOCSIS Network to Offer Symmetric 1Gbps Service Over the Next Two Decades,” Ayham Al-Banna, The NCTA 2012Spring Technical Forum Proceedings, May 21, 2012, hereafter “Al-Banna,”which publication is hereby incorporated herein by reference in itsentirety).

The hardline cable plant of FIG. 2 also may include one or moredirectional couplers 189 (also shown in FIG. 3E) to divide an input RFsignal into two or more RF output signals or combine multiple input RFsignals into one RF output signal (directional couplers also arereferred to as “splitters” or “combiners”). For example, a splitter maydivide an RF signal on one feeder section of the hardline cable plant toprovide respective RF signals on two different feeder sections of thehardline cable plant; conversely, a directional coupler acting as acombiner combines RF signals from respective different feeders onto asame feeder of the hardline plant. In some examples, a directionalcoupler may include a transformer to split or combine power whilemaintaining a certain impedance. In other examples, a directionalcoupler 189 may include various features and materials to reduceinterference. In common implementations, directional couplers arebi-directional devices in which both upstream RF signals and downstreamRF signals may be present, wherein the directional coupler acts as asplitter with respect to downstream RF signals and a combiner withrespect to upstream RF signals as these signals propagate alongdifferent feeder sections of the hardline cable plant.

A distribution tap (or simply “tap”) 188 of the hardline cable plant(see FIG. 3G) provides a connection point between the hardline cableplant and a subscriber service drop 163C. In one aspect, a tap functionssimilarly to a directional coupler in that a small portion of one ormore downstream RF signals on the hardline coaxial cable 163B (e.g., ina “feeder” of the hardline plant) is extracted for providing to asubscriber premises 190. In the upstream direction, taps may beconfigured with different predetermined attenuation values (e.g., 4 dB,11 dB, 17 dB, 20 dB) for attenuating RF signals originating from asubscriber premises 190 (e.g., signals transmitted by the subscribermodem 165) and intended for propagation along the hardline cable plant180 toward the headend 162 of the cable communication system 160. Taps188 may come in various forms, including multi-port taps. Taps typicallyinclude threaded connector ports to facilitate coupling to one or morehardline coaxial cable(s) and one or more subscriber service drops. Incommon examples, a port on a tap to which a subscriber service drop 163Cis coupled may be constituted by a female F-type connector or jack, andthe subscriber service drop 163C includes a coaxial cable terminatedwith a male F-type connector for coupling to the port of the tap 188(e.g., see FIG. 11 and the discussion below in connection with samerelating to male connector 197A and female connector 197B). Thus, in oneaspect, the female F-type connector(s) of one or more taps 188 of thehardline cable plant 180 serve as a “boundary” between the hardlinecable plant and other elements of the cable communication systemgenerally associated with one or more subscriber premises 190.

Line terminators 191 of the hardline cable plant 180 (see FIG. 3C)electrically terminate RF signals at the end of a feeder to preventsignal interference. Line terminators 191 may include various materialsand provide differing levels of shielding from environmental elements.

Various connectors 193 (see FIG. 3B) employed in the hardline cableplant 180, also referred to herein as “fittings,” may join two coaxialcables from separate sheaths, or may join a coaxial cable to one of theelements discussed above (e.g., amplifiers, power supplies, taps,directional couplers, line terminators, etc.). Connectors may be male,female, or sexless; some connectors have female structures with slottedfingers that introduce a small inductance; other connectors involvepin-based structures (e.g., pin-type connectors, such as housingterminators, extension fittings, 90-degree fittings, splice connectors,etc.). One common example of a connector is given by “F” seriesconnectors, which may have ⅜-32 coupling thread or may be push-on. Othertypes of connectors employed in hardline cable plants include UHFconnectors, BNC connectors, and TNC connectors. Various connectorsdiffer in the methods they use for connecting and tightening. A spliceblock 195 (see FIG. 3D) is a particular type of connector used to jointwo respective segments of hardline coaxial cable.

As also shown in FIG. 2, the subscriber service drop 163C generallyrefers to the coaxial cable and associated hardware between adistribution tap 188 and a subscriber premises 190. In one aspect, asdiscussed above, a subscriber service drop 163C may be deemed to “begin”at a male F-connector (coupled to a female F-connector of a distributiontap 188) with which a coaxial cable used for the subscriber service drop163C is terminated (e.g., see FIG. 11, male connector 197A). Asubscriber service drop 163C often is constituted by a coaxial cablesegment of a different type than the hardline coaxial cable 163Bemployed in the hardline plant 180 (as generally shorter cable lengths,greater physical flexibility, and less environmental robustness arerequired for subscriber service drops 163C than for the hardline cableplant 180; also whereas hardline coaxial cable is intended to be anessentially permanent component over the life of a cable communicationsystem, subscriber service drops are considered as less permanent andmay be installed and removed based on service changes relating to newsubscribers or cancellation of services by existing subscribers). Someexamples of coaxial cable conventionally employed for subscriber servicedrops 163C are given by RG-6 and RG-59 cables (e.g., seehttp://www.tonercable.com/assets/images/ProductFiles/1830/PDFFile/TFC%20T10%2059%20Series%20Drop%20Cable.pdf).In other examples, a subscriber service drop 163C may be constituted bya “flooded” cable or a “messenger” (aerial) cable; “flooded” cables maybe infused with heavy waterproofing for use in an underground conduit ordirectly buried in the ground, whereas “messenger” cables may containsome waterproofing as well as a steel messenger wire along the length ofthe cable (to carry tension involved in an aerial drop from a utilitypole). At the subscriber premises 190, the service drop 163C typicallyis fastened in some manner to the subscriber premises 190 and coupled toa ground block 198, and in turn connects to various components insidethe subscriber premises, such as interior cables 192 (each of whichtypically terminates with connectors 196), one or moresplitters/combiners 194, and one or more end user modems 165 (sometimescollectively referred to as “subscriber premises equipment” or “customerpremises equipment”).

Finally, FIG. 2 also illustrates that an analyzer 110 (e.g., a spectrumanalyzer and/or a tuned receiver) may be coupled to a junction betweenthe bridge converter 167 and the hardline cable plant 180 so as tomonitor RF signals that are transmitted to and/or received from thefirst node 164A. The coupling of the analyzer 110 to the junctionbetween the bridge converter 167 and the hardline cable plant 180 isshown in FIG. 2 using dashed lines, so as to indicate that the analyzer110 is not necessarily included as a constituent element of the firstnode, but may be optionally employed from time to time as a testinstrument to provide information relating to signals propagating toand/or from the first node. As discussed further below in connectionwith FIGS. 1 and 4, an analyzer similarly may be employed in the headendto monitor various RF signals of interest in the cable communicationsystem.

Table 1 below provides some typical parameters generally representativeof node architecture found in several conventional communication systems(e.g., see “Mission is Possible: An Evolutionary Approach toGigabit-Class DOCSIS,” John Chapman et al., The NCTA 2012 SpringTechnical Forum Proceedings, May 21, 2012, hereafter referred to as“Chapman,” which publication is hereby incorporated herein by referencein its entirety; pages 35-47 and 57-62 of Chapman discuss particulars ofnode architecture):

TABLE 1 Households Passed (HHP) 500 Subscriber Premises (e.g., highspeed data) 50% HHP Density 75 HHP/mile Node Mileage 6.67 miles CascadeNODE + 5 or +6 Amplifiers/Mile 4.5/mile Taps/Mile 30/mile Amplifiers  30Taps 200 Highest Tap Value 23 dB Lowest Tap Value 8 dB Express FeederCable Type 0.750 inch PIII Largest Express Feeder Span 2000 feet Feeder(distribution) Cable Type 0.625 inch PIII Feeder Cable Distance to FirstTap 100 feet Largest Feeder Span 1000 feet Subscriber Drop Cable TypeSeries 6 Largest Drop Cable Span 150 feet Maximum Subscriber ModemTransmit Power 65 dBmV

Headend

With reference again to FIG. 1, the headend 162 of the cablecommunication system 160 generally serves as a receiving and processingstation at which various entertainment program signals (e.g., televisionand video programming from satellite or land-based sources) arecollected for retransmission to the subscriber premises of respectivenodes 164A, 164B, and 164C over the downstream path bandwidth of eachnode. The headend 162 also may serve as a connection point to variousvoice-based services and/or Internet-based services (e.g., dataservices) that may be provided to the subscriber premises of respectivenodes 164A, 164B, and 164C; such voice-based services and/orInternet-based services may employ both the upstream path bandwidth anddownstream path bandwidth of each node. Accordingly, the headend 162 mayinclude various electronic equipment for receiving entertainmentprogramming signals (e.g., via one or more antennas and/or satellitedishes, tuners/receivers, amplifiers, filters, etc.), processing and/orrouting voice-related information, and/or enabling Internetconnectivity, as well as various electronic equipment for facilitatingtransmission of downstream information to, and receiving upstreaminformation from, the respective nodes. Some conventional cablecommunication systems also include one or more “hubs” (not shown in FIG.1), which are similar to a headend, but generally smaller in size; insome cable communication systems, a hub may communicate with a largerheadend, and in turn provide television/video/voice/Internet-relatedservices only to some subset of nodes (e.g., as few as a dozen nodes) inthe cable communication system.

Since each node of the cable communication system 160 functionssimilarly, some of the salient structural elements and functionality ofthe headend 162 may be readily understood in the context of a singlenode (e.g., represented in FIG. 1 by the first node 164A). Accordingly,it should be appreciated that the discussion below regarding certainelements of the headend 162 particularly associated with the first node164A applies similarly to other elements of the headend that may beassociated with and/or coupled to other nodes of the cable communicationsystem 160.

As shown in FIG. 1, the fiber optic cable 163A of the first node 164A iscoupled to an optical/RF bridge converter 175 within the headend 162(also referred to herein as a “headend optical/RF bridge converter”). Asalso shown in FIG. 1, each of the other nodes 164B and 164C similarly iscoupled to a corresponding optical/RF bridge converter of the headend162. The headend bridge converter 175 functions similarly to the bridgeconverter 167 of the first node; i.e., the headend bridge converter 175converts upstream optical signals carried by the fiber optic cable 163Ato RF signals 177 within the headend 162. In some implementations, theheadend bridge converter 175 is constituted by two distinct devices,e.g., a downstream transmitter to convert RF signals originating in theheadend to downstream optical signals, and an upstream receiver toconvert upstream optical signals to RF signals in the headend. Theheadend 162 also may include an RF splitter 173, coupled to the headendbridge converter 175, to provide multiple paths (e.g., via multipleports of the RF splitter) for the RF signals 177 in the headend that aretransmitted to or received from the headend bridge converter 175. Asdiscussed in greater detail below in connection with FIG. 4, the RFsplitter 173 provides for various equipment (e.g., demodulators,modulators, controllers, test and monitoring equipment) to be coupled tothe RF signals 177 within the headend carrying information to or fromthe first node 164A; for example, FIG. 1 illustrates an analyzer 110(e.g., a spectrum analyzer), coupled to the RF splitter 173, that may beemployed to monitor RF signals 177 in the headend 162 that aretransmitted to and/or received from the first node 164A (as alsodiscussed above in connection with FIG. 2).

The headend 162 shown in FIG. 1 also includes a cable modem terminationsystem (CMTS) 170 that serves as the central controller for thesubscriber modems in respective nodes of the cable communication system160. In general, the CMTS 170 provides a bridge between the cablecommunication system 160 and an Internet Protocol (IP) network andserves as an arbiter of subscriber time sharing (e.g., of upstream pathbandwidth in each node) for data services. In particular, for upstreaminformation transmitted from subscriber modems in a given node to theheadend 162 (e.g., the upstream information 184 from the first node164A), in example implementations the CMTS 170 instructs a givensubscriber modem in a given node when to transmit RF signals (e.g., ontoa corresponding subscriber service drop and the hardline plant of thegiven node) and what RF carrier frequency to use in the upstream pathbandwidth of the node (e.g., the upstream path bandwidth 182 of thefirst node 164A). The CMTS 170 then demodulates received upstream RFsignals (e.g., the RF signals 177 from the first node 164A) to recoverthe upstream information carried by the signals, converts at least someof the recovered upstream information to “outgoing” IP data packets 159,and directs the outgoing IP data packets to switching and/or routingequipment (not shown in FIG. 1) for transmission on the Internet, forexample. Conversely, the CMTS 170 also receives “incoming” IP datapackets 159 from the Internet via the switching and/or routingequipment, modulates RF carrier waves with data contained in thereceived incoming IP data packets, and transmits these modulated RFcarrier waves (e.g. as RF signals 177) to provide at least some of thedownstream information (e.g., the downstream information 183 of thefirst node 164A) to one or more subscriber modems in one or more nodesof the cable communication system.

As also indicated in FIG. 1, in some implementations in which therecovered upstream information includes voice information (e.g., fromsubscriber premises receiving VoIP services), the CMTS 170 may alsodirect “outgoing” voice information 157 to a voice switch coupled to aPublic Switched Telephone Network (PSTN). The CMTS 170 also may receive“incoming” voice information 157 from the PSTN, and modulate thereceived incoming voice information onto RF carrier waves to provide aportion of the downstream information.

As illustrated in FIG. 1, the CMTS 170 may include multiple RF ports 169and 171, in which typically one pair of RF ports 169 and 171 of the CMTSfacilitates coupling of a corresponding node of the cable communicationsystem 160 (in some instances via one or more RF splitters 173) to theCMTS 170; in particular, for the first node 164A shown in FIG. 1,downstream RF port 169 provides downstream information from the CMTS tothe first node, and upstream RF port 171 provides upstream informationto the CMTS from the first node. For each downstream RF port 169, theCMTS further includes one or more modulation tuners 172 coupled to thedownstream RF port; similarly, for each upstream RF port 171, the CMTSincludes one or more demodulation tuners 174 coupled to the upstream RFport 171. As noted above, the modulation tuner(s) 172 is/are configuredto generate one or more modulated RF carrier waves to provide downstreaminformation to subscriber modems of the node coupled to thecorresponding RF port 169; conversely, the demodulation tuner(s) 174is/are configured to demodulate one or more received upstream RF signalscarrying upstream information from the subscriber modems of the nodecoupled to the corresponding RF port 171.

FIG. 4 illustrates further details of a portion of the headend 162 shownin FIG. 1, relating particularly to upstream information received fromsubscriber modems of the first node 164A via the fiber optic cable 163A,and exemplary arrangements of the CMTS 170. For example, FIG. 4 showsthat the RF splitter 173 associated with the first node 164A may includemultiple ports to couple upstream RF signals 177 received from the firstnode to each of the analyzer 110, one RF port 171 of the CMTS 170, adigital account controller 254 (DAC), and other test and/or monitoringequipment 256. The DAC 254 relates primarily to video programming (e.g.,managing on-demand video services by receiving programming requests fromsubscriber premises “set-top boxes” and coordinating delivery ofrequested programming). As discussed elsewhere herein, the analyzer 110may be configured to monitor a spectrum of the upstream path bandwidthto measure an overall condition of the upstream path bandwidth (e.g., apresence of noise in the node) and/or provide performance metricsrelating to the conveyance of upstream information in the node (e.g.,for diagnostic purposes). Other test and/or monitoring equipment 256 maybe configured to receive signals from field-deployed monitoring devices(most typically in power supplies in the node) to alert system operatorsof critical events (e.g., a power outage) or other alarm conditions.

The CMTS 170 itself may be constructed and arranged as a modularapparatus that may be flexibly expanded (or reduced in size) dependingin part on the number of nodes/subscribers to be served by the cablecommunication system 160. For example, the CMTS 170 may have a housingconfigured as a chassis with multiple slots to accommodate“rack-mountable” modular components, and various RFmodulation/demodulation components of the CMTS may be configured as oneor more such modular components, commonly referred to as “blades,” whichfit into respective slots of the CMTS's chassis. FIG. 4 shows a portionof the CMTS 170 including two such “blades” 252.

As illustrated in FIG. 4, each blade 252 of the CMTS 170 may includemultiple upstream RF ports 171 (e.g., four to six ports per blade), aswell as one or more downstream ports (not explicitly shown in FIG. 4).Historically, each upstream RF port 171 of a blade 252 was coupled toonly one demodulation tuner 174 serving a particular node coupled to theupstream RF port 171; in more recent CMTS configurations, a blade 252may be configured such that one or more upstream RF ports 171 of theblade may be coupled to multiple demodulation tuners 174 (e.g., FIG. 4shows two demodulation tuners 174 coupled to one upstream port 171 ofthe top-most blade 252). In this manner, the upstream information from agiven node may be received by the CMTS via multiple RF signals 177(i.e., one RF signal per demodulation tuner 174 coupled to the blade'supstream RF port 171 corresponding to the given node). The CMTS 170 mayinclude virtually any number of blades 252, based at least in part onthe number of nodes included in the cable communication system 160 (andthe number of RF ports per blade).

Various implementations of the CMTS 170 constitute examples of a “cablemodem system,” which generally refers to one or more modulation tunersand/or demodulation tuners, and associated controllers and otherequipment as may be required, to facilitate communication of downstreaminformation to, and/or upstream information from, one or more subscriberpremises. As noted above, one or both of the downstream information andupstream information handled by a cable modem system may include avariety of data content, including Internet-related data, voice-relateddata, and/or audio/video-related data. Other implementations of a cablemodem system may include a “Converged Cable Access Platform” (CCAP),which combines some of the functionality of a CMTS discussed above andvideo content delivery in contemplation of conventional MPEG-based videodelivery migrating to Internet Protocol (IP) video transport (e.g., see“CCAP 101: Guide to Understanding the Converged Cable Access Platform,”Motorola whitepaper, February 2012,http://www.motorola.com/staticfiles/Video-Solutions/Products/Video-Infrastructure/Distribution/EDGE-QAM/APEX-3000/_Documents/_StaticFiles/12.02.17-Motorola-CCAP%20101_white%20paper-US-EN.pdf,which whitepaper is hereby incorporated by reference herein in itsentirety). For purposes of the discussion below, the CMTS 170 isreferred to as a representative example of a “cable modem system;”however, it should be appreciated that the various concepts discussedbelow generally are applicable to other examples of cable modem systems,such as a CCAP.

Communication Concepts

With reference again to FIG. 1, the transmission of downstreaminformation 183 between the headend 162 and subscriber premises 190 inthe first node 164A, and the transmission of upstream information 184from one or more subscriber premises 190 in the first node 164A to theheadend 162, may be understood as follows.

With respect to downstream information 183 in the first node 164A,digital information (e.g., voice information or other data in the formof IP data packets 159 from an external IP network) constituting thedownstream information is modulated onto an RF carrier wave (having aparticular carrier frequency in the downstream path bandwidth 181) by amodulation tuner 172 in the CMTS 170 at the headend 162, to provide adownstream RF signal 177 via a port 171 of the CMTS 170. This downstreamRF signal 177 is converted to a downstream optical signal by headendoptical/RF converter 175 and transported via first fiber optic cable163A to the first optical/RF converter 167 in the first node 164A, whichconverts the downstream optical signal back to an RF signal. Thisconverted RF signal (carrying the downstream information 183) is thentransported via the hardline cable plant 180 and subscriber servicedrops 163C to the respective subscriber modems 165 of the subscriberpremises 190, each of which modems includes appropriate demodulatorcircuitry that is tuned to the carrier frequency of the downstream RFsignal so as to appropriately demodulate the RF signal and therebyrecover the downstream information 183 (e.g., in the form of the IP datapackets 159).

With respect to upstream information 184, the foregoing process isessentially reversed; i.e., digital information originating from a givensubscriber premises 190 (e.g., voice information or other data in theform of IP data packets) constituting at least a portion of the upstreaminformation 184 is modulated onto an RF carrier wave (having aparticular frequency in the upstream path bandwidth 182) by modulationcircuitry in the subscriber modem 165 to provide an upstream RF signal.This upstream RF signal is transported via subscriber service drop 163Cand the hardline cable plant 180 to the first optical/RF converter 167in the first node 164A, which converts the upstream RF signal to anupstream optical signal that is transported to the headend 162 via thefirst fiber optic cable 163A. At the headend, the headend optical/RFconverter 175 converts the upstream optical signal back to an upstreamRF signal 177. This RF signal 177 is coupled via a port 171 of the CMTS170 to a demodulation tuner 174 tuned to the carrier frequency of theupstream RF signal so as to appropriately demodulate the upstream RFsignal and thereby recover the upstream information 184 (e.g., which maybe in the form of IP data packets 159 to be conveyed to an external IPnetwork).

Regarding common modulation schemes that may be employed generally bysubscriber modems 165, or the modulation tuners 172 and demodulationtuners 174 of the CMTS 170 at the headend 162, to encode digitalinformation (e.g., the downstream information 183 and the upstreaminformation 184) on an RF carrier wave to provide an RF signal, suchmodulation schemes often employ modulation of the phase and/or theamplitude of a carrier wave having a given carrier frequencyfbased onthe particular digital information to be encoded. To illustrate somecommon digital modulation schemes, it is helpful to first represent asinusoidal carrier wave having an amplitude A, a frequency f, and aphase φ (in radians), denoted mathematically as A sin (2πft+φ), as thecomposition of two sinusoidal waves that are out of phase by 90 degreeswith respect to each other. Using well-known trigonometricrelationships, it may be shown that:

A sin(2πft+φ)=I sin(2πft)+Q cos(2πft),  Eq. 1

where:

$\begin{matrix}{A = \sqrt{I^{2} + Q^{2}}} & {{Eq}.\mspace{11mu} 2} \\{and} & \; \\{\phi = {{\arctan \left( \frac{Q}{I} \right)}.}} & {{Eq}.\mspace{11mu} 3}\end{matrix}$

The foregoing decomposition of a carrier wave is sometime referred to as“orthogonal decomposition,” in which the sine term of the decompositionis referred to as the “in-phase” component having an amplitude I, andthe cosine term of the decomposition is referred to as the “quadrature”component having an amplitude Q. The representation of a sinusoidalcarrier wave in terms of in-phase and quadrature components may befacilitated by a coordinate plane defined by a horizontal axisrepresenting values of I (the “in-phase component” axis) and a verticalaxis representing values of Q (the “quadrature component” axis). FIG. 5shows a generic example of the carrier wave of Eq. 1 represented as avector on such a coordinate plane, in which the length of the vector isgiven by the amplitude A (according to Eq. 2) and the phase of thevector is given by the angle ca between the vector and the in-phasecomponent axis (according to Eq. 3).

In some digital modulation schemes commonly employed in conventionalcable communication systems, the amplitudes I and Q of the in-phase andquadrature components, respectively, may only have one of some number offinite values at any given time. Once the in-phase and quadraturecomponents are combined according to Eq. 1, each of the possiblecombinations of finite values that the amplitudes I and Q may haveaccording to a given digital modulation scheme correspond to aparticular unique state of the resulting modulated carrier wave, whichstate is defined by a particular amplitude A and a particular phase φ ofthe resulting modulated carrier wave (pursuant to Eq. 2 and Eq. 3above). With the foregoing in mind, each of the possible combinations offinite values that the amplitudes I and Q may have in a given modulationscheme are assigned to some number m bits of digital information to beencoded on the carrier wave; each m bits of digital information that isassigned to a particular combination of I and Q values is commonlyreferred to as a “symbol.” In this manner, each unique combination of mdigital bits (each “symbol”), representing a particular combination ofpossible values for each of I and Q, “maps” to a particular amplitude Aand a particular phase φ of the resulting modulated carrier wave.

More specifically, a given modulator (e.g., modulator circuitry in asubscriber modem 165, or a modulation tuner 172 of the CMTS 170)separates a carrier wave to be encoded into respective in-phase andquadrature components and, based on the respective values (i.e., logic 1or logic 0) of m digital bits in a given symbol to be encoded, selectscorresponding assigned values for the amplitudes I and Q respectively.The in-phase and quadrature components are then recombined and, as notedabove, the resulting modulated carrier wave has a particular amplitude Aand a particular phase ca corresponding to the particular symbol encodedon the wave. A given demodulator employing the same modulation schemeand receiving such a modulated carrier wave (a “signal”) is thus able torecover the particular symbol by determining the amplitude and phase ofthe received signal.

Two common digital modulation schemes employed in conventional cablecommunication systems and based on the foregoing concepts includequadrature phase shift keying (QPSK) and different orders of quadratureamplitude modulation (QAM). With reference again to Eq. 1 above, in QPSKeach of the amplitudes I and Q for the respective in-phase andquadrature components has the same magnitude |X| and one of two possiblenon-zero values at any given time, namely I=+X or −X, and Q=+X or −X. Aconvenient way to visualize a QPSK modulation scheme (as well as otherdigital modulation schemes) is via a “constellation diagram,” in whichdifferent possible states of the recombined (modulated) carrier wave areillustrated in the coordinate plane employed for FIG. 5 (i.e., having ahorizontal “in-phase” axis and a vertical “quadrature” axis). FIG. 6illustrates such a constellation diagram 5000A for a QPSK modulationscheme; again, in QPSK, only values of +X and −X are possible for eachof I and Q. As such, there are four different possible states for theresulting recombined carrier wave, which states commonly are referred toas “constellation points.” An interesting artifact of QPSK is that,since the magnitudes of I and Q are identical at any given time (i.e.,|X|), the amplitude A of the resulting modulated carrier wave remainsfixed according to Eq. 2 (i.e., A=√{square root over (2)}|X|); however,the respective constellation points have different phases φ, namely 45degrees, 135 degrees, 225 degrees and 315 degrees (hence the namequadrature “phase shift” keying). Given the four constellation pointsrepresenting different phases, each point may be represented by a uniquecombination of two bits of digital information constituting a “symbol”corresponding to the constellation point (e.g., “11”=45 degrees;“01”=135 degrees; “00”=225 degrees, and “10”=315 degrees).

Like QPSK, Quadrature Amplitude Modulation (QAM) similarly is based onamplitude modulation of respective in-phase and quadrature components ofa carrier wave, which components are recombined to form aninformation-bearing signal (i.e., a modulated carrier wave). UnlikeQPSK, however, in QAM each of the amplitudes I and Q of the respectivein-phase and quadrature components may have one of multiple differentmagnitudes, resulting in a modulated carrier wave with both changingamplitude A and phase ca. Different QAM schemes may be visualized via aconstellation diagram similar to that shown in FIG. 6 for QPSK. In QAM,the constellation points typically are arranged in a grid with equalvertical and horizontal spacing. The number of constellation points in agiven square-grid QAM implementation is often referred to as the QAM“modulation order” and is related to the number n of unique magnitudeseach of the I and Q amplitudes may have. If the value of n for the Iamplitudes is different than the number n for Q amplitudes, arectangular-shaped constellation diagram results; if on the other handthe number n of unique magnitudes is the same for both I and Q), asquare constellation diagram results. Rectangular QAM constellationsgenerally are sub-optimal in that constellation points are not maximallyspaced for a given constellation energy, and they are somewhat morechallenging to modulate and demodulate. Accordingly, square QAMconstellations are more commonly (but not exclusively) employed inconventional cable communication systems, wherein the QAM modulationorder is given by:

QAM modulation order=4n ².  Eq. 4

From Eq. 4, it may be appreciated that the QPSK constellation diagramshown in FIG. 6 is actually a special case of QAM with modulation order4 (i.e., n=1 results in 4-QAM).

The number of constellation points in a given QAM implementation alsodictates the number of unique symbols that may be mapped to theconstellation diagram, which in turn depends on the number of bits persymbol m; i.e., the number of unique symbols=2̂^(m) (m=1, 2, 3 . . . ).Again, since QAM often is implemented as a square-grid constellationdiagram (e.g., see Eq. 4), certain QAM modulation orders are morecommonly implemented in conventional cable communication systems, forvalues of m>2 and integer values of n that satisfy:

QAM modulation order=4n ²=2̂^(m).  Eq. 5

Table 2 below lists some common QAM modulation orders and associatedvalues of n (number of unique magnitudes of I and Q) and m (number ofbits per symbol) for square QAM constellations based on Eq. 5. Table 2also includes entries for 32-QAM and 128-QAM and their associated bitsper symbol m; these are rectangular constellations (for which there isno integer value for n in Eq. 5) that nonetheless may be employed insome cable communication system implementations. To illustrate thehigher QAM modulation orders for square constellations listed in Table2, FIG. 7 provides an example constellation diagram 5000B for 16-QAM,FIG. 8 provides an example constellation diagram 5000C for 64-QAM, andFIG. 9 provides an example constellation diagram 5000D for 256-QAM.

TABLE 2 QAM modulation order (symbols per constellation) n m 4 1 2 16 24 32 5 64 4 6 128 7 256 8 8 512 9 1024 16 10 2048 11 4096 32 12

Although Table 2 and FIGS. 7 through 9 illustrate four exemplarymodulation orders for QAM, it should be appreciated that pursuant to thegeneral principles outlined above, a number of different QAM modulationorders are possible in addition to those noted in Table 2 and FIGS. 7through 9. In general, by moving to a higher QAM modulation order it ispossible to transmit more bits per symbol. However, for purposes ofcomparing two different QAM modulation orders, if the mean energy of theconstellation is to remain the same, the respective constellation pointsmust be closer together within the constellation. Recall that eachconstellation point represents a particular amplitude A and phase φ of amodulated carrier signal that ultimately needs to be demodulated by ademodulator (that can effectively discern amongst different points ofthe constellation). As discussed further below in connection with FIG.16, noise that may be present on a physical communication mediumcarrying a QAM signal may alter one or both of the amplitude A and phaseφ of the signal such that the signal, upon demodulation, may be confusedwith another neighboring point on the constellation, resulting in thewrong symbol being recovered by a demodulator. As respectiveconstellation points are more “tightly-packed” in higher modulationorder constellations, they are thus more susceptible to noise and othercorruption upon demodulation; accordingly, higher modulation-order QAMcan deliver more data less reliably than lower modulation-order QAM, forconstant mean constellation energy.

Turning again to FIG. 1, and with respect to communication of upstreamand downstream RF signals associated with the first node 164A within theheadend 162, on the hardline plant 180, or on the subscriber servicedrops 163C, each of the downstream path bandwidth 181 and the upstreampath bandwidth 182 is divided up into multiple communication “channels”to convey the downstream information 183 and the upstream information184. For purposes of the present disclosure, a “physical communicationchannel” may be described by at least three parameters, namely: 1) acarrier frequency of an RF carrier wave onto which information (e.g.,upstream information 184 or downstream information 183) is modulated; 2)a modulation type (e.g., QPSK, QAM), used by a modulation tuner 172 atthe headend or modulation circuitry of a subscriber modem 165, tomodulate the carrier wave; and 3) a channel bandwidth, wherein thecarrier frequency typically is located at a center of the channelbandwidth. As discussed in detail further below, another parameter of anupstream physical communication channel may include the access protocol(e.g., Time Division Multiple Access, Advanced Time Division MultipleAccess, Synchronous Code Division Multiple Access) employed to transportupstream information from multiple subscriber premises via the physicalcommunication channel.

Regarding physical communication channel parameters, as noted above theupstream path bandwidth 182 in the United States typically includesupstream channels having carrier frequencies within a first frequencyrange of from 5 MHz to 42 MHz (5 MHz to 65 MHz in Europe), and thedownstream path bandwidth 181 includes downstream channels havingcarrier frequencies within a second frequency range of from 50 MHz to750 MHz (and in some instances as high as approximately 1 GHz). Asdiscussed in greater detail below, practical considerations relating tonoise have limited the information carrying capacity of the upstreampath bandwidth in the portion of the spectrum between approximately 20MHz and 42 MHz, and have rendered the portion of the upstream pathbandwidth between 5 MHz and approximately 20 MHz effectively unusable.Accordingly, upstream channels having carrier frequencies in the rangeof 5 to approximately 20 MHz (and particularly below 18 MHz, and moreparticularly below 16.4 MHz, and more particularly below 10 MHz) arerarely if ever employed in conventional cable communication systems; ifused at all, such channels are typically limited to rudimentary binarymodulation schemes (e.g., binary phase-shift keyed or “PSK” modulation,or binary frequency-shift keyed or “FSK” modulation) rather thanquadrature modulation schemes, and have significantly limitedinformation-carrying capacity and functionality (e.g., conveyingsubscriber orders for pay-per-view television from subscriber premisesto the headend of the cable communication system).

With respect to the bandwidth of physical communication channels,typical upstream and downstream channel bandwidths employed for cablecommunication system channels are 3.2 MHz and 6.4 MHz, although otherchannel bandwidths are possible (e.g., 1.6 MHz). Conceptually, thebandwidth of a physical communication channel for which QPSK or QAMmodulation schemes are employed effectively represents the number ofsymbols per second that may be conveyed over the channel, which in turnrelates to the maximum data rate of the channel. According to variouschannel filtering and tuning techniques which define the passband (i.e.,shape or profile) of a channel as a function of frequency, only aportion of the stated bandwidth of a channel is available for datatransmission (e.g., the lowest and highest frequency portions of thechannel serve as transition bands and the centermost frequencies of thechannel serve as a passband); thus, it is conventionally presumed thatapproximately 80% of the stated bandwidth of a given channel is deemedavailable for data transmission. Accordingly, the “symbol rate” of agiven channel (i.e., the maximum number of symbols per second that canbe effectively conveyed over the channel) is taken to be 80% of thechannel's specified bandwidth. With the foregoing in mind, a maximum“deployed data rate” (also sometimes referred to as “raw data rate”)with which the upstream information 184 or the downstream information183 may be conveyed on a given physical communication channel (“datarate” is also sometimes referred to as “channel capacity”) is typicallyspecified in units of bits per second and is based on the symbol rate ofthe channel (0.8 BW) and the number m of bits per symbol (as dictated bythe modulation order), given by:

Data rate(bits/sec)=0.8 BW(symbols/sec)*m(bits/symbol).  Eq. 6

Using values of m from Table 2 above corresponding to different QAMmodulation orders (wherein 4-QAM=QPSK), FIG. 10 illustrates a bar graphshowing different modulation orders and channel bandwidths along thehorizontal axis, and corresponding maximum deployed (or “raw”) datarates along the vertical axis, according to Eq. 6. From FIG. 10, it maybe seen that a conventional 6.4 MHz channel in which a 64-QAM modulationscheme is used may convey data at a maximum deployed data rate ofapproximately 30 Mbits/s.

As an alternative to the graph of FIG. 10, the maximum deployed datarates for respective QAM modulation orders may be normalized fordifferent possible channel bandwidths, in units of bits/sec-Hz (byremoving the BW term from Eq. 6). Table 3 below provides the normalizedmaximum “raw” data rates for different QAM modulation orders, and thecorresponding maximum raw data rates (maximum deployed channelcapacities) for channel bandwidths of 1.6 MHz, 3.2 MHz and 6.4 MHz,respectively, corresponding to each QAM modulation order:

TABLE 3 QAM modulation Raw Data 1.6 MHz BW 3.2 MHz BW 6.4 MHz BW order(symbols Rate/Hz Raw Data Rate Raw Data Rate Raw Data Rate perconstellation) m (bps/Hz) (Mbits/s) (Mbits/s) (Mbits/s) QPSK (4-QAM) 21.6 2.56 5.12 10.24  16-QAM 4 3.2 5.12 10.24 20.48  32-QAM 5 4.0 6.4012.80 25.60  64-QAM 6 4.8 7.68 15.36 30.72  128-QAM 7 5.6 8.96 17.9235.84  256-QAM 8 6.4 10.24 20.48 40.96  512-QAM 9 7.2 11.52 23.04 46.081024-QAM 10 8.0 12.80 25.60 51.20 2048-QAM 11 8.8 14.08 28.16 56.324096-QAM 12 9.6 15.36 30.72 61.44

With reference again to FIG. 1, it should be appreciated that in theconventional cable communication system 160, downstream information 183in the first node 164A generally is broadcast from the headend 162,using multiple downstream channels having different carrier frequenciesin the downstream path bandwidth 181, to all subscriber premises 190 inthe node; however, the demodulator circuitry of a given subscriber modem165 generally is tuned to only one or more particular carrierfrequencies in the downstream path bandwidth 181 at a given time so asto recover only a particular portion of the downstream information 183(i.e., particular downstream information encoded on an RF signal havinga carrier frequency to which the modem's demodulator is tuned).

Conversely, multiple subscriber premises 190 in the node 164A typicallyshare a single upstream channel defined by an RF signal having a carrierfrequency in the upstream path bandwidth 182, so as to convey respectiveportions of upstream information 184 originating from differentsubscriber modems 165 that share the upstream channel. A collection ofmultiple subscriber premises/subscriber modems of a given node thatshare a single upstream channel commonly is referred to as a “servicegroup” (in FIG. 1, such a service group is denoted by reference number195; in some conventional cable communication systems, a service groupmay include between approximately 100 and 300 subscriber premises). Toensure that upstream information from multiple subscriber modems in aservice group is effectively received at the headend, various upstream“access protocols” may be implemented by the CMTS 170 and the subscribermodems 165 to regulate the manner in which portions of upstreaminformation from different subscriber modems are carried over the sharedupstream channel. Examples of such access protocols include TimeDivision Multiple Access (TDMA), Asynchronous Transfer Mode (ATM),Carrier Sense Multiple Access/Collision Detection (CSMA/CD). Generallyspeaking, such access protocols are responsible for implementing timingschemes with which different subscriber modems may transmit portions(“transmission bursts”) of upstream information, and in some casesassigning a carrier frequency to be modulated (with upstreaminformation) by the modulation circuitry of a subscriber modem.

One widely adopted specification for transport of upstream anddownstream information via a cable communication system and associatedaccess protocols is referred to as the “Data Over Cable ServiceInterface Specification” (DOCSIS). DOCSIS is an international openprotocol developed by the industry consortium CableLabs for deployinghigh-speed data and voice services over cable communication systemssimilar to the system 160 shown in FIG. 1. The DOCSIS specificationrelates to aspects of the “physical layer” of the communication system(e.g., specifying channel bandwidths and modulation types supported),the “data link layer” of the communication system (e.g., specifyingaccess protocols for transmission of upstream information, quality ofservice features to support Voice-over-Internet Protocol, or “VoIP,” andchannel bonding), and the “network layer” of the communication system(e.g., management of subscriber modems and the CMTS via IP addresses).

More specifically, with respect to “physical layer” specifications, theNorth American version of DOCSIS utilizes 6 MHz channels fortransmission of downstream information, and specifies upstream channelbandwidths of between 200 kHz and 3.2 MHz (DOCSIS version 1.0) and morerecently 6.4 MHz (DOCSIS versions 2.0 and 3.0). All versions of DOCSISspecify that 64-QAM or 256-QAM may be used for modulation of downstreaminformation; DOCSIS version 1.0 specified QPSK or 16-QAM for modulationof upstream information, and DOCSIS versions 2.0 and 3.0 specify QPSK,8-QAM, 16-QAM, 32-QAM, and 64-QAM for modulation of upstream information(where noise conditions permit such higher modulation orders, asdiscussed further below). DOCSIS versions 2.0 and 3.0 also supports alimited special version of 128-QAM for modulation of upstreaminformation, requiring trellis coded modulation in Synchronous CodeDivision Multiple Access (S-CDMA) mode (discussed further below). Withrespect to “data link layer” or media access control layer (MAC)specifications, DOCSIS employs a mixture of deterministic access methodsfor transmission of upstream transmission, specifically TDMA for DOCSISversion 1.0/1.1 and both ATDMA (Advanced Time Division Multiple Access)and S-CDMA for DOCSIS versions 2.0 and 3.0. For DOCSIS 1.1 and above thedata link layer also includes quality-of-service (QoS) features tosupport applications that have specific traffic requirements such as lowlatency (e.g., VoIP, some gaming applications). DOCSIS version 3.0 alsofeatures channel bonding, which enables multiple downstream and upstreamchannels to be used together at the same time by a single subscribermodem.

DOCSIS also defines a “channel utilization index” which generallyrepresents a percentage of time over some predetermined time period thatthe respective subscriber premises of a service group are transmittingupstream information and hence “using” the physical communicationchannel over which upstream information from the service group isconveyed. More specifically, the upstream channel utilization index isexpressed as a percentage of minislots utilized on the physicalcommunication channel, regardless of burst type. In one example,minislots are considered utilized if the CMTS receives an upstream burstfrom any subscriber modem transmitting on the physical channel. Inanother example (“contention REQ and REQ/DATA”), minislots for atransmission opportunity are considered utilized if the CMTS receives anupstream burst within the opportunity from any subscriber modemtransmitting on the physical channel.

Egress and Ingress

A cable communication system is considered theoretically as a “closed”information transmission system, in that transmission of informationbetween the headend 162 and subscriber modems 165 occurs via thephysical communication media of optical fiber cable, a hardline cableplant, and subscriber service drops (and not over air or “wirelessly”)via prescribed portions of frequency spectrum (i.e., in the U.S.,upstream path bandwidth from 5 MHz-42 MHz; downstream path bandwidthfrom 50 MHz to 750 MHz or higher). In practice, however, cablecommunication systems generally are not perfectly closed systems, andmay be subject to signal leakage both out of and into the system (e.g.,through faulty/damaged coaxial cable and/or other network components).The term “egress” refers to signal leakage out of a cable communicationsystem, and the term “ingress” refers to signal leakage into a cablecommunication system. A significant operating and maintenance expensefor owners/operators of cable communication systems relates toaddressing the problems of signal egress and ingress.

More specifically, egress occurs when RF signals travelling in thedownstream path bandwidth of a cable communication system leak out intothe environment. Egress may cause RF interference with devices in thevicinity of the point of egress, and in some cases can result in weakersignals reaching the subscriber modems 165. The Federal CommunicationsCommission (FCC) enforces laws established to regulate egress, notingthat egress may cause interference with “safety-of-life” radio services(communications of police, fire, airplane pilots) and endanger the livesof the public by possibly hampering safety personnel's efforts.Accordingly, the FCC has set maximum individual signal leakage levelsfor cable communication systems. As a further prevention, the FCCrequires cable communication system operators to have a periodicon-going program to inspect, locate and repair egress on their systems.

In light of the potential for catastrophic harm which may be caused bycable communication system egress interfering particularly withaeronautical navigational and communications radio systems, the FCCrequires more stringent regulations for cable communication systemegress in the aeronautical radio frequency bands (sometimes referred toas the “aviation band,” from approximately 110 MHz to 140 MHz). Forexample, any egress in the aviation band which produces a field strengthof 20 uV/m or greater at a distance of three meters must be repaired ina reasonable period of time. Due to these regulations and governmentoversight by the FCC, cable communication system operators historicallyhave focused primarily on egress monitoring and mitigation.

With respect to examples of conventional techniques for detectingegress, the company Comsonics, Inc. (http://www.comsonics.com/) providesvarious equipment (e.g., a GPS navigation system, an RF receiver, and anRF antenna), referred to as Genacis™, for a vehicle-based approach tomonitor egress over a geographic region. In particular, the Genacis™ RFantenna monitors one or more particular frequencies in the downstreampath bandwidth of the cable communication system generally correspondingto the aviation band (e.g., approximately 120 MHz) and records signalamplitude of any egress emanating from the cable communication system atthe monitored frequency and vehicle position. This information is usedto identify locations of egress in the network.

Ingress is noise or interference that may occur from an outside signalleaking into the cable communication system infrastructure. The sourceof the outside signal is commonly referred to as an “ingress source.”Some common ingress sources include broadband noise generated by variousmanmade sources, such as automobile ignitions, electric motors, neonsigns, power-line switching transients, arc welders, power-switchingdevices such as electronic switches and thermostats, and home electricalappliances (e.g., mixers, can openers, vacuum cleaners, etc.) typicallyfound at subscriber premises. Although some of these ingress sourcesproduce noise events in the 60 Hz to 2 MHz range, their harmonics mayshow up in the cable communication system upstream path bandwidth from 5MHz to 42 MHz. “Impulse” noise is generally characterized by arelatively short burst of broadband noise (e.g., 1 to 10 microseconds),and “burst” noise is generally characterized by bursts of broadbandnoise with durations up to about 100 microseconds. In addition tomanmade sources of broadband noise which may contribute to burst orimpulse noise, natural sources of burst noise include lightning andelectrostatic discharge, which may give rise to noise events from 2 kHzup to 100 MHz.

Other ingress sources include relatively narrowband signals arising fromtransmission sources that may be proximate to the cable communicationsystem (e.g., transmitting devices such as HAM or CB radios in thevicinity, subscriber premises garage door openers, fire and emergencycommunication devices, and pagers). In particular, ham radio operatorsuse carrier frequencies at 7 MHz, 10 MHz, 14 MHz, 18 MHz, 21 MHz, 24 MHzand 28 MHz, and citizen band radios use frequencies at approximately 27MHz, all of which fall within the upstream path bandwidth of the cablecommunication system.

The foregoing ingress sources often create intermittent and/or seeminglyrandom signals that may leak into the infrastructure of the cablecommunication system, causing disturbances that may be difficult tolocate and/or track over time. Such disturbances may impede normaloperation of the cable communication system, and/or render somecommunication bandwidth significantly compromised or effectivelyunusable for conveying information. In particular, ingress from theserandom and/or intermittent sources may undesirably and unpredictablyinterfere with transmission of upstream information by operative RFsignals in the upstream path bandwidth. Yet another ingress sourceincludes “terrestrial” signals present in free space, primarily fromshort wave radio and radar stations (e.g., short wave radio signals arepresent from approximately 4.75 MHz to 10 MHz).

It is commonly presumed in the cable communication industry that egressmay serve as a proxy for ingress; i.e., where there is an opening/faultin the cable communication system that allows for signal leakage fromthe system to the outside (egress), such an opening/fault likewiseallows for outside signals to enter the cable communication system(ingress). It is also commonly presumed in the cable communicationindustry that a significant majority of cable communication systemfaults allowing for signal leakage into and out of the system occuralmost entirely in connection with system elements associated with oneor more subscriber premises; more specifically, subscriber servicedrops, and particularly subscriber premises equipment, areconventionally deemed to be the greatest source of signal leakageproblems.

FIG. 11 shows the example subscriber premises 190 from FIG. 2, togetherwith a portion of the hardline cable plant 180 including two segments ofhardline coaxial cable 163B and a tap 188, to which the segments ofhardline coaxial cable 163B are coupled via connectors 193. A subscriberservice drop 163C also is coupled to the tap 188, for example, via amale connector 197A on one end of the subscriber service drop 163C and afemale connector 197B of the tap 188. As illustrated in FIG. 11, it iscommonly presumed in the cable communication industry that approximately75% or more of ingress in a cable communication system originates insiderespective subscriber premises 190 (all subscriber premises taken inaggregate), and that approximately 20% is attributable to the respectivesubscriber service drops 163C (taken in aggregate) (e.g., see “ReturnPath Maintenance Plan: A Five Step Approach to Ensuring a ReliableCommunications Path,” Robert Flask, Acterna LLC whitepaper, 2005, page7,http://sup.xenya.si/sup/info/jdsu/white_papers/ReturnPathMaintenancePlan_Whitepaper.pdf).

More specifically, poorly shielded subscriber premises equipment (e.g.,defective or inferior quality cables 192; loose, corroded, orimproperly-installed connectors 196; improperly terminated splitters194), together with faults associated with the subscriber service drop163C (e.g., pinched, kinked, and/or inferior quality/poorly shieldedcable 163C; loose, corroded, or improperly-installed drop connectors197A to the tap 188; improper/poor ground block splices 198), areconventionally deemed to account for 95% or more of ingress in the cablecommunication system (i.e., 75% inside subscriber premises plus 20%subscriber service drop, as noted above). While the hardline cable plant180 generally is considered to be significantly better shielded andmaintained (e.g., by the cable communication system owner/operator), incontrast the respective subscriber premises 190 typically are the leastaccessible and least controllable (i.e., they are generally privateresidences or businesses) and, as such, the least regularly-maintainedportion of the cable communication system 160 (i.e., there is no regularaccess by the system owner/operator); hence, subscriber premises andtheir associated service drops are generally considered in the industryto be the most susceptible to signal leakage problems. Faults insubscriber service drops 163C and/or within subscriber premises 190 areconsidered to readily permit ingress from common ingress sources oftenfound in household devices (e.g., appliances, personal computers, otherconsumer electronics, etc.) of cable communication system subscribers,as well as other ingress sources (e.g., garage door openers, varioustransmitting devices such as HAM or CB radios in the vicinity, fire andemergency communication devices, and terrestrial signals).

With respect to conventional ingress mitigation techniques, someapproaches involve installing passive filters (e.g., in the taps 188 orwithin subscriber premises 190) to attenuate ingress originating fromsubscriber premises, while other approaches involve active systems thatmonitor communication traffic on the upstream path bandwidth andattenuate all or a portion of this bandwidth during periods of idletraffic. These approaches do not attempt to identify or eliminateingress sources, but merely attempt to reduce their impact, and areaccordingly not completely effective. Some other approaches, discussedin detail below, do attempt to identify subscriber-related faults thatallow for ingress, but are generally labor and/or time intensive andlargely ineffective. Furthermore, given the conventional presumptionthat 75% or more of ingress problems are deemed to relate to faultsinside subscriber premises, even if ingress sources of this ilk areidentified they may not be easily addressed, if at all (e.g., it may bedifficult or impossible to gain access to one or more subscriberpremises in which faults giving rise to ingress are suspected).

One conventional method for detecting ingress is to sequentiallydisconnect respective sections of hardline coaxial cable 163B(“feeders”) within the hardline cable plant 180 in which suspectedingress has been reported (e.g., by disconnecting a given feeder branchfrom the port of a directional coupler 189), and concurrently monitorresulting variations in the noise profile of the upstream path bandwidthas seen from the headend of the network (e.g., using the analyzer 110shown in FIGS. 1, 2 and 4). This technique is sometimes referred to as a“divide and conquer” process (e.g., akin to an “Ariadne's thread”problem-solving process), and entails a significantly time consumingtrial-and-error approach, as there are often multiple hardline coaxialcable feeder branches ultimately serving several subscriber premises,any one or more of which could allow for ingress to enter the network;accordingly, this technique has proven to be inaccurate and inefficientat effectively detecting points of ingress. Additionally, disruptiveconventional methods involving disconnecting different feeder cables inthe hardline cable plant cause undesirable subscriber interruption ofordinary services, including one or more of entertainment-relatedservices, data and/or voice services, and potentially critical services(i.e. lifeline or 911 services).

Other conventional approaches to ingress mitigation employ lowattenuation value switches (termed “wink” switches), installed indifferent feeder branches of the hardline cable plant, to selectivelyattenuate noise in the upstream path bandwidth and thereby facilitatelocalizing potential sources of ingress. Each wink switch has a uniqueaddress, and the various switches are sequentially controlled tointroduce some amount of attenuation in the corresponding branch. Theupstream path bandwidth is monitored at the headend (e.g., via theanalyzer 110) while the wink switches are controlled, allowingobservation at the headend for any changes in noise level in theupstream path bandwidth that may be attributed to respectivecorresponding branches. In one aspect, the use of wink switches in thisapproach constitutes an essentially automated methodology of theapproach described immediately above (i.e., “divide and conquer”), butsuffers from the same challenges; namely, the feeder branches beingselectively attenuated ultimately serve several subscriber premises, anyone or more of which could allow for ingress to enter the network.Accordingly, pinpointing potential points of ingress remains elusive.

In yet other conventional approaches, mobile transceivers may beemployed in an attempt to detect both egress and ingress. For example,U.S. Pat. No. 5,777,662 (“Zimmerman”), assigned to Comsonics, Inc.,discloses an ingress/egress management system for purportedly detectingboth ingress and egress in a cable communication system. The systemdescribed in Zimmerman includes a mobile transceiver that receives RFegress and records GPS coordinates. The mobile transceiver alsotransmits a signal that is modulated with GPS coordinates. If there is asignificant fault in the cable communication system allowing for ingressin the vicinity of signal transmission, the transmitted signal may bereceived at the headend of the network by a headend monitoring receiver.Based on transmitted signals that are received at the headend, acomputer assigns coordinates to potential flaws within the cable systemto generate a simple point map of same so that they may be repaired by atechnician. One disadvantage of this system is that the transmittedsignal modulated with GPS coordinates must be received at the headendwith sufficient strength and quality to permit identification of thelocation of a potential flaw; in other words, if a potential flaw is notsignificant enough so as to admit the transmitted signal with sufficientstrength, but is nonetheless significant enough to allow some amount ofingress to enter into the system, no information about the location ofthe potential flaw is received at the headend. Thus, obtaining anaccurate and complete profile of potential ingress across a range ofsignal levels (and across a significant geographic area covered by acable communication system), arguably is significantly difficult toachieve (if not impossible) using the techniques disclosed in Zimmerman.

It is generally understood that noise levels due to ingress in theupstream path bandwidth may vary as a function of one or more of time,frequency, and geographic location. Conventional ingress detection andmitigation techniques generally have been marginally effective inreducing ingress to some extent in the upper portion of the upstreampath bandwidth (e.g., above 20 MHz); however, notable ingress noiselevels continue to persist below approximately 20 MHz, with ingressnoise at the lower end of this range (e.g., 5 MHz to approximately 18MHz, and particularly below 16.4 MHz, and more particularly below 10MHz) being especially significant.

As a result, it is widely accepted in the cable communication industrythat only a portion of the upstream path bandwidth of a cablecommunication system, generally from about 20 MHz to 42 MHz, may be usedin some circumstances (e.g., depending in part on the presence ofbroadband noise and/or narrowband interference, carrier frequencyplacement of one or more communication channels, carrier wave modulationtype used for the channel(s), and channel bandwidth) for transmission ofupstream information from subscriber modems to the headend, and that thelower portion of the upstream path bandwidth (e.g., generally from about5 MHz to about 20 MHz, and particularly below 18 MHz, and moreparticularly below 16.4 MHz, and more particularly 10 MHz) iseffectively unusable due to persistent ingress.

FIG. 12 shows an example of a power spectral density (PSD) (or“spectrum”) 2100A associated with the upstream path bandwidth 182 (i.e.,5 MHz to 42 MHz for the U.S.) of a conventional cable communicationsystem, so as to illustrate the presence of ingress. The spectrum 2100Ashown in FIG. 12 is provided as a screen shot from a display of aspectrum analyzer at the headend or coupled to the hardline cable plant180 (e.g., serving as the analyzer 110 discussed above in connectionwith FIGS. 1, 2 and 4). In the spectrum analyzer screen shot of FIG. 12,the horizontal axis represents frequency in MHz, and the vertical axisrepresents signal level in dBmV.

As illustrated in FIG. 12, the presence of significant ingressdisturbances 3500 from 5 MHz to just above approximately 20 MHz may bereadily observed in the spectrum 2100A, including what appear to be anumber of narrowband interference signals (also referred to as discrete“ingress carriers”) at approximately 6-7 MHz, 9 MHz, 10 MHz, 11.5 MHz,13 MHz, 15 MHz, 18 MHz and 21 MHz, respectively (viewed from left toright in the screen shot). As noted above, constituent elements of suchingress disturbances 3500 possibly may be due to ham radio, short waveterrestrial signals, or other sources of narrowband interference thathas entered via one or more faults. The spectrum 2100A in FIG. 12 alsoillustrates the presence of two channels 2103A and 2103B in the upstreampath bandwidth 182, placed in a relatively “cleaner” portion of thespectrum 2100A at carrier frequencies of approximately 25 MHz and 30MHz, respectively, wherein each upstream channel has a bandwidth 2109 of3.2 MHz. From the relative signal levels of the channels 2103A and 2103Bas compared to the ingress disturbances 3500, it may be readilyappreciated from FIG. 12 that the ingress disturbances 3500 in theregion of the spectrum 2100A below approximately 20 MHz essentiallypreclude the existence of any channels in this portion of the upstreampath bandwidth.

FIG. 13 shows another example of a spectrum 2100B associated with theupstream path bandwidth 182 of a conventional cable communicationsystem, so as to illustrate the presence of ingress in the form ofbroadband impulse noise (see Chapman, pages 90-91). As illustrated inFIG. 13, the presence of broadband impulse noise 3502 (indicated by adashed oval in FIG. 13) covers a significant portion of the upstreampath bandwidth 182 and is likely adversely impacting the transmission ofupstream information via the channel 2103C (having a carrier frequencyof approximately 27 MHz). As noted above, ingress sources giving rise tosuch broadband impulse noise 3502 include electric motors andpower-switching devices (often found in household devices at subscriberpremises).

FIG. 14 shows yet another example of a spectrum 2100C associated withthe upstream path bandwidth 182 of a conventional cable communicationsystem, so as to illustrate the presence of ingress. The screen shot ofthe spectrum 2100C shows a frequency marker at 50 MHz, around whichfrequency point (e.g., from about 40 MHz to 54 MHz) a significant“roll-off” may be readily observed in the spectrum 2100C (e.g., due todiplex filters included in amplifiers of the hardline cable plant),indicating the transition between the upstream path bandwidth 182 andthe downstream path bandwidth (i.e., above 50 MHz). By conventionalstandards, the spectrum 2100C represents an example of a relatively“clean” upstream path bandwidth (see pages 31-33, FIG. 19 of “DigitalTransmission: Carrier-to-Noise Ratio, Signal-to-Noise Ratio, andModulation Error Ratio,” Ron Hranac and Bruce Currivan, Ciscowhitepaper, November 2006,http://www.cisco.com/en/US/prod/collateral/video/ps8806/ps5684/ps2209/prod_white_paper0900aecd805738f5.html,hereafter “Hranac,” which whitepaper is hereby incorporated herein byreference in its entirety). In particular, the “noise floor” 2107 of thespectrum 2100C is relatively flat from about 25 MHz to 42 MHz. Forpurposes of the present disclosure, the noise floor of a spectrum refersto a measure of additive white Gaussian noise (AWGN) power (sometimesalso referred to as “thermal noise” or “white noise”) within ameasurement bandwidth of an instrument providing the spectrum. A noisefloor may be substantially flat across a significant range offrequencies covered by the spectrum, or may vary within differentfrequency ranges of a given spectrum. In the example of FIG. 14, thenoise floor 2107 is relatively flat from about 25 MHz to 40 MHz (thereappears to be a very slight decrease in the noise floor over this range,but overall the noise floor is relatively flat in this range).Notwithstanding, below 25 MHz and particularly below 20 MHz, the noisefloor rises significantly, and additionally the presence of significantingress disturbances 3500 may be observed in the spectrum 2100C,including what appear to be a number of discrete “ingress carriers” atfrequencies similar to those shown and discussed above in connectionwith FIG. 12.

While the particular regions of the spectrums 2100A and 2100C associatedwith ingress disturbances 3500 including discrete ingress carriers areparticularly noteworthy in FIGS. 12 and 14, it should be appreciatedthat ingress may more generally impact the overall spectrum of theupstream path bandwidth; in particular, as illustrated in FIG. 13,various sources of ingress beyond the more discrete carriers shownamongst the ingress disturbances 3500 in FIGS. 12 and 14 may serve aswider-band noise sources that contribute to the overall noise profile ofa spectrum, throughout significant portions (if not substantially allof) the spectrum.

The spectrum 2100C of FIG. 14 also illustrates the presence of anupstream channel 2103D in the upstream path bandwidth 182, wherein theupstream channel has a bandwidth 2109 of 3.2 MHz and is placed at acarrier frequency of 32.75 MHz (i.e., within a “cleaner” portion of thespectrum 2100B). A “carrier-to-noise ratio” (CNR) 2105 of the upstreamchannel 2103D also is indicated in FIG. 14; generally speaking, asdiscussed in greater detail below, a larger CNR for a channel (i.e., agreater distance between the average channel power, as represented bythe top of the “haystack” profile for the channel, and the noise floorof the spectrum proximate to the channel) typically correlates with areasonably functioning channel that effectively conveys upstreaminformation, whereas relatively smaller values for CNR may be associatedwith channels that are not capable of conveying upstream informationwith sufficient reliability or accuracy. Accordingly, at least from aqualitative perspective, it may be appreciated from FIG. 14 that even ina so-called “clean” upstream spectrum by conventional standards, thepresence of significant ingress disturbances 3500 in the region of thespectrum 2100C below approximately 20 MHz (notwithstanding therelatively lower magnitude of these disturbances as compared to FIG. 12)nonetheless poses significant challenges for the placement ofappropriately functioning upstream channels in this region of thespectrum (e.g., see Table 4 and Table 5 discussed below).

Noise-Based Limitations on Cable System Communications

As noted above, noise that may be present on one or more physicalcommunication media of a cable communication system may corrupt theintegrity of information-bearing signals propagating on themedia/medium. More specifically, as discussed above in connection withFIGS. 12 through 15, ingress in the upstream path bandwidth of a cablecommunication system can significantly (and adversely) impact the amountof usable spectrum within the upstream path bandwidth that can beemployed to effectively convey upstream information from subscriberpremises to the headend.

In the cable communication industry, various figures of merit are usedto characterize the communication of information via modulated RFcarrier waves (i.e., RF signals) in the presence of noise on thecommunication medium/media over which the RF signals propagate. Adetailed treatment of such figures of merit is found in Hranac,referenced above.

One such figure of merit discussed in Hranac is referred to as“Carrier-to-Noise Ratio” (CNR), which is defined as the ratio of carrieror signal power to white-noise power in a specified bandwidth, asmeasured on a spectrum analyzer (or similar equipment). CNR often isexpressed in units of decibels (dB), according to the relationship:

$\begin{matrix}{{{{CNR}\mspace{14mu} ({dB})} = {10\; {\log \left( \frac{P_{{carrier}/{signal}}}{P_{noise}} \right)}}},} & {{Eq}.\mspace{11mu} 7}\end{matrix}$

where P_(carrier/signal) is the carrier or signal power in Watts, andP_(noise) is the additive white Gaussian noise (AWGN) power in Wattsover a specified bandwidth. For digitally modulated RF signals (e.g.,QPSK and QAM signals), the signal power P_(signal) is the average powerlevel of the signal (also sometimes called average “digital channelpower”) and is measured in the full occupied bandwidth of the signal(i.e., the symbol rate bandwidth, as discussed above in connection withEq. 6).

With reference again to the upstream channel 2103D shown in FIG. 14, thespectrum of a typical QPSK or QAM channel resembles a “haystack” with anessentially flat top across the channel bandwidth. In the spectrum 2100Cof FIG. 14, the height of the channel 2103 gives the signal density inunits of dBmV as measured in the spectrum analyzer resolution bandwidth(RBW) (which in the example of FIG. 14 is 300 kHz). Given the specifiedchannel bandwidth 2109 of 3.2 MHz, this RBW value can be scaled to thesymbol rate bandwidth (i.e., 0.8×3.2 MHz=2.56 MHz) to arrive at thesignal density in the channel (i.e., across the symbol rate bandwidth).Similarly, the height of the noise floor 2107 gives the noise density inunits of dBmV as measured in the spectrum analyzer resolution bandwidth(RBW), and this also can be scaled to the symbol rate bandwidth toprovide the total noise density in the channel. Given decibel units forthe signal power and the noise power as expressed by the spectrumanalyzer, the CNR is calculated by subtracting the total noise densityin the channel from the signal density in the channel—however, sincethese respective values are both scaled similarly by the symbol ratebandwidth, this difference can be read directly from the spectrumanalyzer screen shot as the vertical height between the average value atthe top of the “haystack” channel spectrum to the noise floor, as shownby the reference numeral 2105 in FIG. 14 (In FIG. 14, the CNR 2105 isapproximately 36 dB). This type of measurement of CNR from a spectrumanalyzer screen shot is sufficiently accurate for CNR values greaterthan about 15 dB; if, however, the height between the top of the channelspectrum to the noise floor is between about 10 dB and 15 dB, an offsetof about 0.5 dB should be subtracted from the observed height to providea more accurate CNR measurement (for even smaller heights, largeroffsets are required, e.g., subtracting as much as 1.5 dB from heightsof about 5 dB).

Regarding channel power for upstream channels, and with reference againfor the moment to FIG. 1, as discussed above a number of subscribermodems 165 that share a same physical communication channel in theupstream path bandwidth are referred to a “service group,” and therespective modulator circuits of these modems in the service grouptransmit upstream RF signals at different times (according to TDMA/ATDMAaccess protocols dictated by the CMTS 170 and the modems 165). Althoughtransmitting at different times, subscriber modem upstream transmitlevels are managed by the CMTS 170 so as to provide generally the samereceive level for all subscriber modems (typically with less than 1 dBsignal level difference among the modems) at a given demodulation tuner174 of the CMTS tuned to demodulate the channel. Ingress (as well asAWGN) travels back to this same demodulation tuner, so the noiseamplitude at the CMTS port coupled to the demodulation tuner is the samefor all modems of the service group. Accordingly, the CNR for each modemin a service group (as observed at the CMTS port corresponding to theservice group) typically is substantially similar if not virtuallyidentical to other modems in the service group (unless there is aproblem with a particular subscriber modem and/or an associatedsubscriber-related fault in a subscriber service drop or subscriberpremises equipment within the service group).

Another related figure of merit discussed in Hranac is“Carrier-to-Noise-Plus-Interference Ratio” (CNIR), which makes adistinction between an essentially flat noise floor and more narrowbandnoise that could be present within the bandwidth of a physicalcommunication channel. Rather than taking the ratio of the averagechannel power to only the white noise power in the symbol ratebandwidth, for CNIR the power of any narrowband interference present inthe symbol rate bandwidth is added to the white noise power in thesymbol rate bandwidth, and then the ratio of the channel power to this“noise-plus-interference power” is taken. The noise-plus-interferencepower may be measured during periods in which there is no RF signalbeing transmitted in the channel (“quiet times”); of course, it may beappreciated that for intermittent, random and/or bursty ingress sources,the noise-plus-interference power measurements may differ significantlyas a function of time. In any event, the presence of significantinterference power within the symbol rate bandwidth of a channel, inaddition to white noise power, results in a CNIR significantly lowerthan a comparable CNR in the absence of such interference.

To illustrate the concept of CNIR relative to CNR, FIG. 15 shows thespectrum 2100C of FIG. 14 in which, for purposes of illustration, twoadditional hypothetical channels similar to the 3.2 MHz-wide channel2103D are shown in “phantom” (with dashed lines to outline the channel)on the spectrum 2100C; in particular, a first hypothetical channel 2111is placed at a center frequency of approximately 14 MHz, and a secondhypothetical channel 2113 is placed at a center frequency ofapproximately 11 MHz. These two hypothetical channels occupy a portionof the spectrum 2100C in which the ingress disturbances 3500 arepresent, which disturbances would constitute a significant source ofnoise power in each of the hypothetical channels. In particular, it maybe readily observed in FIG. 15 that the noise floor in the region of thespectrum corresponding to the two hypothetical channels 2111 and 2113 isnotably higher than the noise floor 2107 in the vicinity of the channel2103D (e.g., approximately 3 to 5 dB higher), and the respective peaksof the ingress carriers within the channels (constituting part of theingress disturbances 3500) range from approximately 15 to 20 dB higherthan the noise floor 2107; accordingly, the CNIR for each of the twohypothetical channels 2111 and 2113 would be significantly less than theCNR 2105 of the channel 2103D (e.g., CNIR on the order of 20-23 dB, asopposed to a CNR of 36 dB).

With reference again to the spectrum 2100A shown in FIG. 12, or thespectrum 2100B shown in FIG. 13, the situation for placing hypotheticalchannels in the region of the spectrum 2100A occupied by the ingressdisturbances 3500, or the spectrum 2100B occupied by broadband impulsenoise 3502, would be dramatically worse in terms of CNIR as compared tothe situation discussed immediately above in connection with therelatively “cleaner” spectrum 2100C of FIG. 14. In FIG. 12, therespective CNRs of the channels 2103A and 2103B appear to be somewhatlarger than the CNR 2105 for the channel 2103D shown in FIG. 14(although the spectrums for the channels 2103A and 2103B in FIG. 12 maybe obscuring some underlying narrowband interference noise, which indeedseems to be present to some extent in the region between the channels2103A and 2103B, and just to the left of the channel 2103A). However, ifthe hypothetical channels of FIG. 15 where to be placed in the region ofthe spectrum 2100A in FIG. 12 that is occupied by the ingressdisturbances 3500, or placed virtually anywhere within the spectrum2100B of FIG. 13 below 27 MHz, the CNIR for these hypothetical channelswould be severely lower than the CNR for the channels 2103A and 2103B(at one point around 10 MHz in the spectrum 2100A, there is an ingresscarrier that is only about 3 dB below the channel power of the channels2103A and 2103B).

On this qualitative basis alone, it would be readily appreciated fromFIGS. 12 through 15 that the presence of significant broadband noise andnarrowband interference signals in the region of the spectrum occupiedby the ingress disturbances 3500 or the broadband impulse noise 3502,even for a relatively “clean” upstream spectrum as shown in FIG. 14,effectively precludes the placement of appropriately functioningchannels in this region of the spectrum. As noted in Hranac, on page 6,DOCSIS specifies a minimum CNR for upstream channels, i.e., digitallymodulated carriers, of 25 dB; this level of CNR, however, does notappear to be available for channels that would be placed below 20 MHz inthe spectrums shown in FIGS. 12 through 15.

Table 4 below provides conventionally-accepted minimumcarrier-to-in-channel noise values (CNR or CNIR, denoted generally asC/N) for a given physical communication channel that are required tosupport effective transport and demodulation of information carried overthe channel using a particular modulation order of QAM; stateddifferently, different modulation orders of QAM require differentminimum C/N values (e.g., see Chapman, page 38, Table 4 and page 133,Table 36; also see page 7, Table 3 of “The Grown-up Potential of aTeenage PHY,” Dr. Robert Howald et al., The NCTA 2012 Spring TechnicalForum Proceedings, May 21, 2012, hereafter “Howald,” which publicationis hereby incorporated herein by reference in its entirety; also seeFIG. 1, page 150 of “256-QAM For Upstream HFC,” Thompson et al., NCTA2010 Spring Technical Forum Proceedings, Los Angeles, Calif., May 2010,hereafter “Thompson,” which publication is hereby incorporated herein byreference in its entirety):

TABLE 4 Uncoded Theoretical Operator Desired QAM Modulation Order C/N(dB) C/N Target (db) QPSK (4-QAM) 16 22 16-QAM 22 28 32-QAM 25 31 64-QAM28 34 128-QAM  31 37 256-QAM  34 40In Table 4, the “uncoded theoretical” values for C/N presume a bit errorrate (BER) for demodulated symbols on the order of 10⁻⁸ (BERis the ratioof corrupt bits to total bits of information recovered from demodulationover some sampling period). Also, the uncoded theoretical values for C/Nin Table 4 presume that no forward error correction or “FEC” (discussedin greater detail below) is employed in the transmission of informationvia a given physical communication channel (some MSOs tolerate a pre-FECBER on the order of 10⁻⁷, although as noted above a pre-FEC BER on theorder of 10⁻⁸ ismore commonly adopted as a minimum BER threshold; modemstypically start to have difficulty when BER is as high as on the orderof 10⁻⁶ and modems typically fail to lock consistently when BER is ashigh as on the order of 10⁻⁵; for post-FEC BER, 10⁻⁹ is more commonlyadopted as a minimum acceptable BER threshold for MSOs providing voiceand/or data services, and more specifically “triple play” premiumservices).

The “operator desired” C/N targets listed in Table 4 are chosen toprovide 6 dB of headroom above the uncoded theoretical values (toaccount for a wide variety of possible noise profiles that may occur inactual implementations with upstream information traffic from subscriberpremises). From the C/N values provided in Table 4, it may be furtherappreciated in connection with FIGS. 12 through 15 that the presence ofsignificant broadband noise and narrowband interference signals in theregion of the spectrum occupied by the ingress disturbances 3500 or thebroadband impulse noise 3502, even for a relatively “clean” upstreamspectrum as shown in FIG. 14, effectively precludes the placement ofappropriately functioning channels in this region of the spectrum havinga QAM modulation order greater than 4 (i.e., only QPSK channels mightfunction, if at all, in the lower portion of the upstream pathbandwidth).

While CNR and CNIR (collectively C/N) provide illustrative figures ofmerit relating to RF signals as received by a demodulation tuner in thepresence of noise (in terms of respective signal and noise powers),other instructive figures of merit relate to how effectively receivedsignals are demodulated by a demodulation tuner of the CMTS. Forexample, other figures of merit quantify how effectively received RFsignals are demodulated so as to recover the digital informationtransported by such signals, based on the symbol constellationsassociated with the modulation type and order used to generate the RFsignals.

More specifically, as discussed above in connection with FIGS. 5 through9 relating to QAM constellations and a QAM RF signal carrying upstreaminformation (in which an amplitude A and phase φ of the signal is mappedto a particular point on the constellation corresponding to a symbolrepresenting the upstream information), the presence of noise on amedium carrying such a signal may alter one or both of the signal'samplitude A and phase ca. Such alteration to the signal's amplitude Aand/or phase ca may distort the signal such that, upon demodulation, thedemodulated signal may be mapped not to the “target” constellation pointcorresponding to the original symbol carried by the signal, but insteadto another neighboring point in the constellation, resulting in thewrong symbol being recovered by the demodulator.

FIG. 16 illustrates the effect of noise on the demodulation of QAMsignals (e.g., as may be observed at a demodulation tuner 174 of theCMTS 170 at the headend 162—see FIG. 4) using an example of a QPSK or4-QAM constellation diagram 5000A. As used in connection with FIG. 16,the term “decision boundary” refers to a bounded area on theconstellation diagram 5000A, defined by certain ranges of values for Iand Q, that are used to evaluate the constellation point/symbol of theconstellation diagram to which a received and demodulated RF signal mostappropriately maps. To this end, vertical and horizontal linesrepresenting particular values of I and Q, respectively, are added tothe constellation diagram 5000A so as to separate respective equidistantconstellation points, thereby creating four squares in the constellationdiagram, wherein a corresponding constellation point is at the center ofeach square. Each of the four squares constitutes a decision boundaryfor the corresponding constellation point/symbol, one of which decisionboundaries is labeled in FIG. 16 with the reference numeral 5102 (i.e.,the decision boundary in the top right hand corner of the constellationdiagram 5000A).

Ideally, all received RF signals corresponding to a particularconstellation point/symbol would, upon demodulation, map to the centerof a decision boundary for the constellation point/symbol on theconstellation diagram. However, various imperfections in thecommunication system, giving rise to the presence of noise within thesignal's bandwidth and/or adversely affecting the propagation of the RFsignal along the physical communication media in the system (i.e., the“channel response”), may cause the mapping of the signal upondemodulation to deviate from the center of the decision boundary. Basedon the constellation's decision boundaries, a received RF signal havingan amplitude A and a phase φ which upon demodulation provides I and Qvalues that fall within a particular decision boundary is deemed torepresent the symbol corresponding to the constellation point withinthat decision boundary. Accordingly, such decision boundaries allow fora certain amount of fluctuation in the amplitude A and the phase φ of areceived RF signal due to noise, without resulting in a demodulationerror (or “symbol decoding error”).

In FIG. 16, this behavior may be observed by noting that within eachdecision boundary of the QPSK constellation diagram 5000A, there aremultiple mapped points that fall outside of a shaded circle forming asmall area around the center of each decision boundary. As more pointsare mapped to the constellation diagram over time, the mapped pointsform a “cloud” or “cluster” around the center of each decision boundary.Generally speaking, the amount of noise present within the channeland/or the channel response affects the overall spread of mapped points(spread of the “cloud” or “cluster”) within each decision boundary; insome cases, significant fluctuations in the amplitude A and/or the phaseφ of a received RF signal due to noise in the channel and/or otheradverse affect of the channel response may, upon demodulation, cause oneor more points to be mapped close to or across a boundary edge, thelatter resulting in a symbol decoding error. From FIG. 16, and withreference again to the various constellation diagrams shown in FIGS. 7through 9 for different modulation orders of QAM, it may be appreciatedthat more dense constellations have smaller areas for the decisionboundary associated with each constellation point/symbol; hence, asdiscussed above, RF signals based on higher order QAM modulationgenerally are more susceptible to noise-induced demodulation or symboldecoding errors.

To quantify the spread of mapped points in the example of FIG. 16, thefirst decision boundary 5102 shows a “target symbol vector” 5104, a“received symbol vector” 5106, and an “error vector” 5108 for one ofseveral points mapped to this region of the constellation diagram 5000A.The target symbol vector 5104 represents an “ideal RF signal” that, upondemodulation, would be mapped to the center of the decision boundary5102. The received symbol vector 5106 represents an actual signal thatis received, demodulated, and mapped to the constellation diagram, andthe error vector 5108 represents the difference between the receivedsymbol vector 5106 and the closest target symbol vector 5104. As may beappreciated from FIG. 16, for each received demodulated signal mapped tothe constellation diagram, a corresponding error vector may bedetermined based on the difference between the received symbol vectorcorresponding to the mapped point and the closest target symbol vectorfor the constellation point to which the signal is mapped. Thus, it mayalso be appreciated from FIG. 16 that smaller error vectors correspondto a more accurate mapping of received signals to the constellationdiagram.

The term “modulation error ratio” (MER) refers to a figure of merit,based at least in part on error vectors similar to the error vector 5108shown in FIG. 16, for quantifying the effectiveness of demodulating areceived QAM RF signal. The MER takes into account any noise presentwithin the channel bandwidth as well as the channel response, andprovides a numerical metric to describe the spread (or “fuzziness”) ofthe “cloud” or “cluster” of points mapped to the constellation diagramaround respective constellation points/symbols of the diagram.

Mathematically, MER is defined in terms of the average symbol power ofsome number N of symbols decoded from samples of demodulated received RFsignals, divided by the average error power associated with the decodedsymbols, according to the relationship:

$\begin{matrix}{{{MER}\mspace{11mu} ({dB})} = {10\; {{\log\left\lbrack \frac{\sum\limits_{j = 1}^{N}\; \left( {I_{j}^{2} + Q_{j}^{2}} \right)}{\sum\limits_{j = 1}^{N}\; \left( {{\delta \; I_{j}^{2}} + {\delta \; Q_{j}^{2}}} \right)} \right\rbrack}.}}} & {{Eq}.\mspace{11mu} 8}\end{matrix}$

Again, in Eq. 8 N denotes the total number of symbols determined fromdemodulation of successive samples of a received RF signal over a giventime period, I_(j) and Q_(j) respectively represent the in-phase andquadrature parts of the target symbol vector in the decision boundary towhich the j^(th) sample of the RF signal maps, and δI_(j) and δQ_(j)respectively represent the in-phase and quadrature parts of the errorvector corresponding to the actual point to which the j^(th) sample ofthe RF signal maps. In practical application of Eq. 8, it is presumedthat the measurement of MER is taken over a sufficiently large number Nof samples (e.g., N>100) such that all of the constellation symbols areequally likely to occur; if this is the case, the numerator of Eq. 8divided by N essentially represents the average symbol power of theconstellation as a whole (which is a known constant for a given QAMmodulation order). With this in mind, MER alternatively may be moregenerally defined as the ratio of average constellation symbol power toaverage constellation error power. In general, a higher value for MERrepresents a smaller cloud or tighter cluster of points for each symbol(less “fuzziness”), and corresponds to a lower level of impairments tothe channel (e.g., noise and/or channel response anomalies) that mayadversely impact propagation and hence demodulation of RF signals.

Another figure of merit that is closely related to MER is referred to as“error vector magnitude” (EVM). By convention, EVM is based on theroot-mean-square (RMS) values of error vectors similar to the errorvector 5108 shown in FIG. 16, as a percentage of the maximum symbolmagnitude (e.g., corresponding to the constellation corner states).Accordingly, in contrast to MER, a lower EVM percentage value representsa smaller cloud or tighter cluster of points for each symbol (less“fuzziness”), and corresponds to a lower degree of impairment to thechannel that may adversely impact demodulation of received RF signals.EVM is a linear figure of merit whereas MER is a logarithmic figure ofmerit, but both figures convey similar information regarding theeffectiveness and accuracy of demodulation of QAM RF signals. Forpurposes of the discussion herein, MER is used primarily as the figureof merit regarding demodulation of QAM RF signals; however, it should bereadily appreciated that MER may be converted to EVM, and vice versa,via well-known mathematical relationships (e.g., see Hranac, pages28-29).

With reference again to FIGS. 1 and 4, whereas CNR or CNIR measurementsfor a given upstream channel often are made with the assistance of theanalyzer 110 (e.g., a spectrum analyzer) at the headend 162 (or coupledto the hardline cable plant 180 as shown in FIG. 2), MER measurementstypically are provided by the demodulation tuners 174 of a conventionalCMTS 170 (or in some instances a specialized QAM analysis device/toolmay be employed, e.g., the PathTrack™ HCU200 Integrated Return PathMonitoring Module offered by JDSU, seehttp://www.jdsu.com/ProductLiterature/hcu200_ds_cab_tm_ae.pdf). Adetailed discussion of demodulation tuner functionality and the mannerin which MER measurements may be made is discussed in Hranac (e.g., seeHranac, pages 19-21).

Recall from the discussion above in connection with FIGS. 1 and 4 thatmultiple subscriber premises typically share a single upstream channelas a “service group.” In exemplary implementations of conventionaldemodulation tuners 174 and subscriber modems 165 according to theDOCSIS standard utilizing TDMA or ATDMA, different subscriber premisesof a given service group transmit their corresponding portions ofupstream information to the headend as transmission “bursts” with somepreordained timing (in this context, a demodulation tuner 174 also issometimes referred to as a “burst receiver”). Typical demodulationtuners of a CMTS are configured to report various operating parameters,including MER (some instruments refer to MER as “signal-to-noise ratio”(SNR) as well as “receive modulation error ratio” (RxMER)). Some CMTSsare configured to report MER on both a per-channel basis and aper-subscriber-modem basis, in which per-channel MER measurementsprovide an average MER value over some number of valid bursts from theservice group (DOCSIS specifies upstream MER measurements as an estimateprovided by a CMTS demodulation tuner of the ratio of averageconstellation energy with equally likely symbols to average squaredmagnitude of error vectors, over some number of valid bursts fromdifferent subscriber modems of the service group sharing the physicalcommunication channel assigned to the demodulation tuner). Accordingly,unless otherwise indicated herein, any reference to numerical MER valuesrepresents an MER value for a physical communication channel, ratherthan for a particular subscriber modem (that may be sharing the channelwith other modems of the service group).

Various other features that may be implemented in demodulation tuners174 of the CMTS 170 and subscriber modems 165 adopting DOCSIS version1.1 and higher also may need to be considered in connection with MERmeasurements provided by a given demodulation tuner (or QAM analysisdevice), as they may provide “processing gains” to improve channelperformance in the presence of noise or other channel impediments (e.g.,see “Advanced Physical Layer Technologies for High-Speed Data OverCable,” Cisco Whitepaper, August 2005,http://www.cisco.com/en/US/prod/collateral/video/ps8806/ps5684/ps2209/prod_white_paper0900aecd8066c6cc_ps4969_Products_White_Paper.html,hereafter “Cisco Advanced PHY,” which whitepaper is incorporated byreference herein in its entirety; also see “QAM Overview andTroubleshooting Basics for Recently digital Cable Operators,” JDSUwhitepaper, October 2009,http://www.jdsu.com/ProductLiterature/Digital_QAM_Signals_Overview_and_Basics_of_Testing.pdf,hereafter “JDSU QAM Overview,” which whitepaper is hereby incorporatedby reference herein in its entirety; also see Hranac, pages 18-21). Forexample, subscriber modems 165 may implement an adaptive equalizer(sometimes referred to as a “pre-equalizer”) to intentionally distortthe waveform of a transmitted upstream RF signal so as to compensate forthe upstream channel frequency response; similarly, demodulation tunersmay implement a complimentary adaptive equalizer to compensate forchannel response effects (e.g., group delay variation, amplitude slopeor ripple, and/or microreflections). While the adaptive equalizers inone or both of the subscriber modem and the demodulation tuner maysignificantly improve the channel response for a given channel overwhich upstream information is being communicated, there are practicallimitations on the extent to which channel impairments can becompensated. Notwithstanding, some demodulation tuners of conventionalCMTSs (as well as various QAM analysis devices) provide “equalized” MERmeasurements (i.e., for which a given demodulation tuner adapts itsequalizer on each data traffic burst received from a subscriber modem ofthe service group), as well as “unequalized” MER measurements (e.g., forwhich adaptive equalization is bypassed or not enabled). For purposes ofthe present disclosure, unless otherwise indicated specifically, anyreference to numerical MER values herein presumes an “unequalized” MERmeasurement (which is typically a lower numerical value than acorresponding equalized MER measurement for the same channel, absent theprocessing gain provided by adaptive equalization).

Additionally, some conventional demodulation tuners of CMTSs areequipped with “ingress cancellation” circuitry, which is designed toattenuate to some degree in-channel narrowband interference arising fromingress (as discussed above in the previous section). Such circuitry issimilar to the adaptive equalizers discussed immediately above, in thatit dynamically detects and measures in-channel narrowband interferenceand adapts filter coefficients so as to try to attenuate thedetected/measured interference. Ingress cancellation circuitry may addsome broadband white noise (AWGN) to the channel; additionally, ingresscancellation circuitry generally is only effective at mitigating somedegree of demodulation error due to narrowband interference in a channelthat is already “minimally functioning” (e.g., channels having a CNIRabove a certain minimum threshold, in which there may be a singlenarrowband ingress carrier having relatively modest peak power withinthe channel bandwidth, which may be further attenuated by the ingresscancellation circuitry).

As noted above, however, the presence of appreciable interference (e.g.,in the form of multiple ingress carriers of significant strength—seeFIGS. 12 and 14; and/or broadband impulse noise—see FIG. 13) in someportion(s) of the spectrum of the upstream path bandwidth (e.g., below20 MHz, and particularly below 18 MHz, and more particularly below 16.4MHz, and more particularly below 10 MHz) may significantly impair, orpreclude the existence of, a channel within that/those portion(s) of thespectrum, even with demodulation tuners that employ ingress cancellationcircuitry. Indeed it has been noted that while ingress cancellationcircuitry is effective at facilitating reliable transmissions in themiddle to high end of the upstream path bandwidth, in contrast ingresscancellation circuitry generally is not effective below 20 MHz, wherechannels are most vulnerable to broadband impulse noise (and multiplesignificant ingress carriers) (e.g., see Chapman, page 69; also seeCisco Advanced PHY, pages 23-28, in which tests of ingress cancellationcircuitry for a 16-QAM 3.2 MHz bandwidth channel below 20 MHz result insignificant bit error rates (BER)—ping losses of 0.01% and higher,suggest BERs on the order of 10⁻⁴ to 10⁻⁶, i.e., notably worse BERs thanconventionally acceptable post-FEC BER on the order of 10⁻⁹; also seeThompson, pages 148-149—“Laboratory Measurements”).

With respect to the effect of ingress cancellation circuitry on MER,assuming a minimally functioning channel (e.g., pre-FEC BER on the orderof no higher than 10⁻⁷ and preferably on the order of 10⁻⁸), MERmeasurements for a given channel in which ingress cancellation circuitryis employed generally are higher than CNIR measurements for the channel,due to some degree of attenuation of limited narrowband interference. Inany event, for purposes of the present disclosure, the function ofingress cancellation circuitry, if present in a demodulation tuner ofthe CMTS, is treated similarly to adaptive equalization; accordingly,unless otherwise indicated specifically, again any reference tonumerical MER values herein presumes an “unequalized” MER measurement(in which neither ingress cancellation circuitry nor other adaptiveequalization is employed in connection with demodulation of a receivedupstream RF signal). Again, as noted above, an unequalized MERmeasurement for a channel typically provides a lower numerical valuethan a corresponding equalized MER measurement in which ingresscancellation and/or adaptive equalization is employed.

With the foregoing in mind, there are conventionally-acceptedapproximate minimum unequalized MER values (“MER failure thresholdvalues”) for a given physical communication channel that are required tosupport effective transport and demodulation of information carried overthe channel using a particular modulation order of QAM; stateddifferently, different modulation orders of QAM require different MERfailure threshold values (e.g., see “Broadband: Equalized orUnequalized? That is the Question,” Ron Hranac, CommunicationTechnology, Feb. 1, 2007,http://www.cable360.net/print/ct/operations/bestpractices/21885.html,hereafter “Hranac 2007,” which article is hereby incorporated byreference herein in its entirety; also see Hranac, page 23, Table 4;also see JDSU QAM Overview, pages 7-8). Table 5 below providesrepresentative unequalized MER failure threshold values to supportdifferent modulation orders of QAM, and corresponding C/N target values(from Table 4 above).

TABLE 5 QAM modulation order Minimum Unequalized (symbols perconstellation) MER (dB) C/N Target (db) QPSK (4-QAM) 10-13 22 16-QAM17-20 28 64-QAM 22-24 34 256-QAM  28-30 40Hranac and Hranac 2007 suggest that unequalized MER values in anoperational system should be kept at least 3 dB to 6 dB above thefailure threshold for the modulation type in use (also see Hranac, page23, footnote 11, which notes that many cable operators use the followingunequalized MER values as minimum operational values: QPSK ˜18 dB;16-QAM ˜24 dB; 64-QAM ˜27 dB; and 256 QAM ˜31 dB; also see Chapman, page77, Table 18, which notes an equalized MER of 37 dB to support a pre-FECerror-free 256-QAM channel in the presence of AWGN, and without ingresscarriers; also see “Pushing IP Closer to the Edge,” Rei Brockett et al.,The NCTA 2012 Spring Technical Forum Proceedings, May 21, 2012, whichpublication is hereby incorporated herein by reference in itsentirety—page 5 notes an MER of 37 dB sufficient to support a modulationorder of 256-QAM).

According to Hranac, CNR, CNIR and MER for a given channel should bevirtually identical in an “ideal” system with no impairment to thechannel other than additive white Gaussian noise (AWGN) and with fulltraffic loading (e.g., see Hranac, page 39); in many practicalimplementations, however, Hranac suggests that for CNR values of between15-25 dB, again where AWGN is the primary channel impairment (i.e.,CNR=CNIR), MER should agree with CNR to within about 2 dB or less.Hranac also points out that the MER of a channel is less than, or atbest equal to, CNR, but never greater than CNR, and that MER may beappreciably less than CNR if significant impairments to the channelbeyond AWGN exist (e.g., ingress disturbances and/or channel responseeffects such as group delay variation, amplitude slope or ripple, and/ormicroreflections). Accordingly, it should be appreciated that the CNRfor a given channel may appear to be relatively high while at the sametime the MER for the channel can be unusually low—however, the conversecan not be true; stated differently, a channel may have a relativelyhigh CNR and low MER, but a channel with a low CNR (or low CNIR) willalways have a correspondingly low MER.

With the foregoing also in mind, and with reference again to FIGS. 12and 14, the presence of significant ingress disturbances 3500 in thespectrums 2100A and 2100C are indicative of notably low prospectiveCNIRs for hypothetical channels placed in this portion of the upstreampath bandwidth, as discussed above in connection with FIG. 15.Accordingly, in view of the relationship between MER and CNR/CNIRdiscussed immediately above, and the MER fault thresholds given in Table5 above, such low prospective CNIRs due to significant ingressdisturbances essentially serve as a “non-starter” for implementation offunctioning channels in this portion of the upstream path bandwidth.

As discussed briefly above, one technique specified in DOCSIS to improvethe robustness of information transmission over a physical communicationchannel in the presence of broadband impulse or burst noise is referredto as “Forward Error Correction” (FEC). FEC typically involves thetransmission of additional data (sometimes referred to as “parity bytes”or “overhead”), together with data packets constituting upstreaminformation from subscriber premises that is encoded on a channel'smodulated carrier, to allow for the correction of bit errors postdemodulation. FEC conventionally is accomplished by adding redundancy tothe transmitted information using a predetermined algorithm. Unlikeadaptive equalization and ingress cancellation circuitry, FEC does notaffect MER measurements; rather, if bit errors do occur as a result ofdemodulation, FEC provides a technique by which such bit errors may becorrected based on the “overhead” or redundancy built into theinformation transported over the channel. In this manner, using FEC aspart of the modulation and demodulation processing of informationtransported over a physical communication channel in which a givenmodulation order of QAM is employed may permit somewhat less stringentC/N or MER threshold values for ensuring reliable channel operation(e.g., the C/N and MER threshold values shown in Table 4 and Table 5 maybe somewhat lower if FEC is employed).

To illustrate the foregoing premise, Table 6 below provides additionalC/N performance targets for different modulation orders of QAM using twodifferent types of FEC, namely, “Reed-Solomon” FEC (commonly employed inconventional subscriber modems and CMTSs, and “Low Density Parity Check”(LDPC) codes, currently proposed for future “next generation”implementations of DOCSIS-compliant modulators and demodulators; seeChapman, pages 119 through 126). For comparison, Table 6 also includesuncoded theoretical C/N values from Table 4 above. From Table 6, it maybe appreciated that employing these forms of FEC provides additionalrobustness against channel impairments, thereby permitting lower C/Nperformance targets for sustaining functional channels (e.g., seeChapman, FIG. 57, page 132, and Table 36, page 133).

TABLE 6 Uncoded Reed-Solomon QAM Modulation Theoretical FEC LDPC CodedOrder C/N (dB) C/N Target (dB) C/N Target (dB) QPSK (4-QAM) 16 10 4 16-QAM 22 16 10  32-QAM 25 19 13  64-QAM 28 22 16  128-QAM 31 25 19 256-QAM 34 28 22  512-QAM 37 31 25 1024-QAM 40 34 28 2048-QAM 43 37 314096-QAM 46 40 34

While providing some degree of enhanced protection against noise-inducederrors, FEC does not work well however if significant impulse noisecreates many demodulation errors in succession (e.g., see “Upstream FECErrors and SNR as Ways to Ensure Data Quality and Throughput,” CiscoWhitepaper, Document ID: 49780, Oct. 4, 2005, which whitepaper isincorporated by reference herein in its entirety). In particular,ingress types that could introduce errors that are uncorrectable via FECinclude excessive impulse noise and/or narrowband interference (e.g.,ingress carriers). As discussed earlier in connection with the C/Nmetrics presented in Table 4, some MSOs tolerate a pre-FEC BER on theorder of 10⁻⁷, although a pre-FEC BER on the order of 10⁻⁸ ismorecommonly adopted as a minimum BER threshold; for channels in which FECis employed, a BER on the order of 10⁻⁹ is more commonly adopted as aminimum acceptable BER threshold. In particularly noisy environments,however, even with FEC, this level of BER may be challenging if notimpossible to attain.

In addition to RS-FEC, DOCSIS versions 2.0 and higher support analternative to the TDMA and ATDMA time-division protocols (employed bymultiple subscriber modems to share a channel as a service group) thatpurportedly is more robust than its TDMA/ATDMA counterparts againstchannel impairments such as broadband impulse noise; as briefly notedabove, this alternative protocol is commonly known as Synchronous CodeDivision Multiple Access (S-CDMA) (see Chapman, pages 88 through 95). InS-CDMA, each symbol of data is multiplied at the modulation tuner (i.e.,transmitter) of a subscriber modem by a spreading code including somenumber of codes, which spreads out each symbol in the time domain by asmuch as 128 times. Accordingly a noise burst that may wipe out many QAMsymbols being transported over an ATDMA channel must have asignificantly longer duration to have the same effect on an S-CDMAchannel. At the same time, there is no reduction in data throughput inan S-CDMA channel, as multiple subscriber modems of a service group maytransmit at the same time (the orthogonal spreading code is used todifferentiate respective transmissions from different modems, which maytransmit simultaneously). While S-CDMA is widely touted as a possiblesolution for deployment of channels in the troublesome portion of theupstream path bandwidth below 20 MHz, it has nonetheless remainedlargely unused in practice by MSOs despite its availability in DOCSIS2.0 and DOCSIS 3.0 certified equipment (e.g., see Chapman, page 89).

Regarding the figures of merit discussed above, the power of an S-CDMAburst depends on the number of codes used in the spreading code;accordingly, S-CDMA presents some challenges for accurate CNR and MERmeasurements at the headend. For purposes of the present disclosure,unless otherwise specifically stated, it is presumed that any numericalCNR, CNIR, or MER values provided herein are associated with channelsimplemented according to TDMA or ATDMA protocols, and not S-CDMA (i.e.,it is presumed that subscriber modems and demodulation tuners of theCMTS are not employing S-CDMA unless specifically noted otherwise).

Given the accepted limitations on the upstream path bandwidth arisingfrom ingress, conventional cable communication systems implement“channel plans” for the upstream path bandwidth that attempt to avoidthe various challenges posed by the presence of ingress (as well asother potential channel impairments). For purposes of the presentdisclosure, a “channel plan” for the upstream path bandwidth of a cablecommunication system refers to the designation of one or more of: 1) anumber of channels occupying the upstream path bandwidth; 2) the carrierfrequency/frequencies at which the channel(s) is/are placed in theupstream path bandwidth; 3) the bandwidth(s) of the channel(s); 4) theQAM modulation order(s) of the channel(s); 5) an operational averagepower level for each channel with respect to the overall power budget ofthe upstream path; and 6) an aggregate deployed or “raw” data rate(deployed capacity) for the channel plan. For example, with referenceagain to FIG. 12, the channel plan for the upstream path bandwidth 182represented by the spectrum 2100A includes the two channels 2103A and2103B, wherein the channel 2103A has a carrier frequency of about 25 MHzand the channel 2103B has a carrier frequency of about 30 MHz, bothchannels have a bandwidth of 3.2 MHz, and both channels use QPSK (4-QAM)for modulation of upstream information conveyed by the channel. For agiven upstream channel plan, an aggregate upstream raw data rate (i.e.,“deployed capacity”) may be calculated based on Table 2 and the bargraph shown in FIG. 10. In particular, for the channel plan shown inFIG. 12, FIG. 10 indicates that a 3.2 MHz wide QPSK channel has a rawdata rate of approximately 5 Mbits/s (and from Table 2, for a QPSKchannel, 1.6 bps/Hz×3.2 MHz=5.12 Mbits/s); therefore, given two channelshaving a raw data rate of approximately 5 Mbits/s each, the deployedupstream capacity of the channel plan shown in FIG. 12 is approximately10 Mbits/s.

Generally speaking, only a portion of the deployed capacity for a givenphysical communication channel, or for a given channel plan, isavailable for transporting upstream information from one or moresubscriber premises. In particular, if forward error correction (FEC) isemployed (which is effectively a given in conventional communicationsystems), some of the available deployed capacity is used for theoverhead involved in FEC; similarly, the transmission of upstreaminformation in bursts of data, and formulation of data into IP datapackets, also involves some administrative overhead that consumes someof the deployed capacity of a given channel/channel plan.

More specifically, the “overhead” or “parity bytes” that are employed inFEC understandably take up a portion of the deployed or “raw” data rateof a physical communication channel that would otherwise be used forupstream information from one or more subscriber premises. For example,in conventional Reed-Solomon FEC implementations, k represents thenumber of data symbols being encoded in a given block of data, nrepresents the total number of coded symbols in the encoded block, and trepresents the symbol-error correcting capability of the code, wheren−k=2t provides the number of parity symbols constituting the “overhead”(i.e., to ensure correction of 8 erroneous symbols, 16 parity symbols of“overhead” is required). Thus, a “code rate” of the FEC, i.e., theportion of the encoded data block effectively constituted by theoriginal k symbols of upstream information being encoded, is given byk/n. Example code rates for FEC commonly employed in conventional cablecommunication systems are on the order of approximately 0.7 to 0.9; forexample, consider an RS-FEC in which k=100, n=116, and t=8, providingfor an FEC code rate of 0.862 (e.g., see Chapman, pages 122-123).Accordingly, the “raw” data rate of a physical communication channelemploying FEC is “discounted” or “de-rated” by an amount correspondingto the FEC code rate (in the foregoing example, approximately an 86%de-rating factor).

There are additional aspects of “DOCSIS overhead,” beyond FEC, thatfurther limit an effective data rate of a physical communicationchannel. For example, DOCSIS “physical layer overhead” (“PHY overhead”)relates to some number of symbols in a transmission burst received atthe CMTS that are dedicated to a preamble and a guard band, therebydiminishing the number of symbols in a burst relating to the actualinformation payload. In exemplary implementations, 40 symbols of a 2048symbol burst may be used for PHY overhead, thereby further reducing aneffective data rate for the channel by a factor of 0.9805. In addition,DOCSIS “media access and control layer overhead” (“MAC overhead”)relates to the number of bytes of information typically included in IPdata packets, packet header sizes, number of headers in a giventransmission burst, and other factors that further reduce an effectivedata rate for the channel, typically by a factor of approximately 0.91(e.g., see Chapman, pages 122-123).

Accordingly, when one considers the cumulative effect of FEC, PHYoverhead, and MAC overhead on the data rate of a physical communicationchannel, the deployed or “raw” data rate of the channel needs to bediscounted or de-rated to provide an effective data rate for upstreaminformation from one or more subscriber premises that is conveyed overthe channel. Given the examples provided above for FEC, PHY Overhead,and MAC Overhead, a representative de-rating factor is on the order of(0.862)×(0.985)×(0.91)≈0.77, or approximately 77% of the deployed or rawdata rate for the channel. In view of the foregoing, for purposes of thepresent disclosure, an “effective data rate” for a physicalcommunication channel (or similarly an “effective upstream capacity” fora channel plan) takes into consideration a cumulative de-rating factorthat is applied to the “raw” data rate of the channel (or the deployedcapacity of the channel plan), wherein the de-rating factor may relateat least in part to FEC overhead and/or DOCSIS overhead. For purposes ofthe present disclosure, unless otherwise indicated in illustrativeexamples, a representative FEC/DOCSIS overhead de-rating factor ofapproximately 0.8 (80%) of the raw data rate of a channel (or thedeployed capacity of a channel plan) is presumed to determine aneffective data rate of the channel (or the effective upstream capacityof the channel plan).

FIG. 17 illustrates a chart showing a typical DOCSIS upstream channelplan 2000A for a conventional cable communication system (e.g., see page6 of “Better Returns from the Return Path Implementing an EconomicalMigration Plan for Increasing Upstream Capacity,” Brian O'Neill and RobHowald, Motorola whitepaper, September 2008,http://www.motorola.com/staticfiles/Video-Solutions/Solutions/Industry%20Solutions/Service%20Providers/Cable%20Operators/Broadband%20Access%20Networks%20(BAN)/Fiber%20Deep/_Documents/Static%20files/Better%20Returns%20from%20the%20Return%20PathWhitepaper92008.pdf,hereafter referred to as “Motorola,” which whitepaper is herebyincorporated by reference herein in its entirety). In the chart of FIG.17, the horizontal axis represents frequency within the upstream pathbandwidth from 5 MHz to 42 MHz, and the vertical axis indicates the QAMmodulation order of a given channel and the associated data rate inMbits/s/MHz (from Table 2 above). As shown in FIG. 17, Motorolaindicates that a typical upstream channel plan 2000A includes twochannels 2002A and 2002B having respective carrier frequencies generallyin a range around 30 MHz to 35 MHz (e.g., well above 20 MHz, below whichingress becomes a salient issue, and well below the diplex filterroll-off of the upstream path bandwidth at 42 MHz). Each of the channels2002A and 2002B has a bandwidth of 3.2 MHz, and uses a QAM modulationorder of 16 (16-QAM). In one aspect, the selection of the QAM modulationorder of 16 for the channels 2002A and 2002B, as well as the appropriatechannel carrier frequencies, is based at least in part on prevailingnoise and/or channel response conditions typically expected in aconventional cable system that give rise to a particular MER failurethreshold value according to Table 5 above (i.e., in the case of 16-QAM,an MER of at least 17 to 20 dB, and preferably 24 dB). The deployedupstream capacity for the channel plan 2000A may be estimated from FIG.17 by considering the two channels, each having a bandwidth of 3.2 MHzand respective data rates of 3.2 Mbits/s/Hz; i.e., 2×3.2×3.2≈20.5Mbits/s. Using a de-rating factor of approximately 80%, this deployedupstream capacity corresponds to an effective upstream capacity ofapproximately 16.4 Mbits/s for the channel plan 2000A.

FIG. 18 illustrates a chart showing another DOCSIS upstream channel plan2000B proposed by Hranac and including a 64-QAM upstream channel (e.g.,see “Broadband: Another Look at Upstream 64-QAM,” Ron Hranac,Communications Technology, Apr. 1, 2009,http://www.cablefax.com/ct/operations/bestpractices/Broadband-Another-Look-at-Upstream-64-QAM_(—)34894.html,hereafter referred to as “Hranac Broadband”). In particular, in theproposed channel plan 2000B, a first channel 2002C has a carrierfrequency of 21.6 MHz, a bandwidth of 6.4 MHz, and uses 64-QAM, and asecond channel 2002D has a carrier frequency between 30-35 MHz (e.g.,approximately 32.5 MHz), a bandwidth of 3.2 MHz, and uses 16-QAM. Forthe proposed upstream channel plan 2000B, Hranac Broadband also suggestsmultiple narrower bandwidth QPSK channels (e.g., three 1.6 MHz-wide QPSKchannels 2002E) placed between 35 MHz and approximately 40 MHz. FromFIG. 18 and Table 2, and with the aid of Table 7 below, it can be seenthat the proposed channel plan 2000B has a deployed upstream capacity ofjust under approximately 50 Mbits/s (corresponding to an effectiveupstream capacity of approximately 39 Mbits/s using an 80% de-ratingfactor):

TABLE 7 Channel BW Raw Data Rate Channel QAM (MHz) (Mbits/s) 64 6.430.72 16 3.2 10.24 4 (QPSK) 1.6 2.56 4 (QPSK) 1.6 2.56 4 (QPSK) 1.6 2.56TOTAL DEPLOYED CAPACITY 48.64

In proposing the channel plan 2000B of FIG. 18, Hranac Broadband notesthat the wider bandwidth 64-QAM channel should be placed below 30 MHz toavoid potential channel impairments in the form of group delay arisingfrom diplex filters associated with one or more amplifiers of thehardline cable plant. In particular, as upstream RF signals travel fromsubscriber modems toward the headend, these upstream signals often passthrough multiple amplifiers of the hardline cable plant, each of whichamplifiers contains diplex filters to only permit passage of RF signalswithin the upstream path bandwidth. Hranac Broadband notes that,although the roll-off of such filters in the area of 42 MHz (asdiscussed above in connection with the spectrum 2100C shown in FIG. 14)is generally considered to only affect signal transmission above 35 MHz,this roll-off nonetheless may adversely affect reliable transmission ofsignals modulated with more dense constellations (e.g., 64-QAM), due todiplex filter-related group delay (which is a cumulative effect that isexacerbated with passage of the signal through a greater number ofamplifiers/filters). Accordingly, Hranac Broadband suggests placement ofthe 64-QAM channel 2002C below 30 MHz, and using lower modulation orderand lower bandwidth channels above 30 MHz (e.g., the channels 2002D and2002E shown in FIG. 18).

FIG. 19 illustrates a chart showing yet another DOCSIS upstream channelplan 2000C proposed by Motorola (see Motorola, page 6) that suggeststhree upstream 64-QAM channels above 20 MHz, and two 16-QAM channelsbelow 20 MHz. The channel plan 2000C proposed by Motorola, however,requires the use of the S-CDMA protocol (as opposed to TDMA or ATDMA)for at least two and possibly three of the upstream channels. Inparticular, in the channel plan 2000C, two channels collectively labeledas 2002F are proposed below 20 MHz, each having a bandwidth of 3.2 MHzand using 16-QAM with S-CDMA (the requirement of S-CDMA is indicated inFIG. 19 using cross-hatching for the channels 2002F). Motorolaacknowledges that, in the upstream path bandwidth, frequencies belowabout 20 MHz, and especially below 15 MHz, tend to be cluttered withinterference and impulse noise (e.g., see the ingress disturbances 3500and broadband impulse noise 3502 shown in FIG. 12-16 as discussedabove), thus making this band unsuitable for DOCSIS performance andunused for DOCSIS services. Motorola nonetheless proposes that lowermodulation order QAM (e.g., 16-QAM), coupled with S-CDMA technology,could be used for channels below 20 MHz.

The proposed channel plan 2000C shown in FIG. 19 also indicates theplacement of a 6.4 MHz-wide 64-QAM channel 2002G above 20 MHz. Motorolaindicates that this channel may be implemented successfully using anATDMA protocol, but also indicates, however, that this channel mayrequire the use of S-CDMA technology for successful implementation(accordingly, the possible requirement of S-CDMA for the channel 2002Gis indicated with “confetti-type” fill in FIG. 19). Motorola furthersuggests that the proposed channel plan 2000C also may include two 6.4MHz-wide 64-QAM channels 2002H employing ATDMA (i.e., without requiringthe use of S-CDMA). It is noteworthy that the placement of thesechannels 2002H as recommended by Motorola would occupy a portion of theupstream path bandwidth well above 30 MHz, in stark contrast to theteachings of Hranac Broadband (which advise against placement of 64-QAMchannels above 30 MHz, at least in part due to undesirable diplexfilter-related group delay effects). In any event, from FIG. 19 andTable 2, and with the aid of Table 8 below, it can be seen that thechannel plan 2000C, which would require the use of S-CDMA for at leasttwo if not three of the specified channels, has a deployed upstreamcapacity of just over approximately 110 Mbits/s (corresponding to aneffective upstream capacity of approximately 90 Mbits/s using an 80%de-rating factor):

TABLE 8 Channel BW Raw Data Rate Channel QAM (MHz) (Mbits/s) 16 (S-CDMA)3.2 10.24 16 (S-CDMA) 3.2 10.24  64 (S-CDMA?) 6.4 30.72 64 6.4 30.72 646.4 30.72 TOTAL DEPLOYED CAPACITY 112.64

FIG. 20 illustrates a chart showing yet another DOCSIS upstream channelplan 2000D proposed by Chapman (see Chapman, page 89, FIG. 37) thatsuggests a total of seven channels, i.e., four ATDMA channels above 22.8MHz and three S-CDMA channels below 22.8 MHz; accordingly, like thechannel plan 2000C shown in FIG. 19 proposed by Motorola, Chapman'sproposed channel plan also requires S-CDMA channels below 20 MHz.Specifically, below 22.8 MHz, Chapman's channel plan 2000D calls for a32-QAM S-CDMA channel 20021 having a bandwidth of 3.2 MHz, another32-QAM S-CDMA channel 2002J having a bandwidth of 6.4 MHz, and a 64-QAMS-CDMA channel 2002K having a bandwidth of 6.4 MHz. Above 22.8 MHz,Chapman's proposed channel plan 2000D calls for two 64-QAM ATDMAchannels 2002L each having a bandwidth of 6.4 MHz, a 64-QAM ATDMAchannel 2002M having a bandwidth of 3.2 MHz, and a 16-QAM ATDMA channel2002N having a bandwidth of 3.2 MHz (notably, Chapman's proposed channelplan 2000D adopts in part the recommendation of Hranac Broadband againstplacement of 64-QAM channels above 30 MHz, by using the smallerbandwidth 16-QAM channel 2002N closest to the diplex filter roll-off atthe highest end of the spectrum).

From FIG. 20 and Table 2, and with the aid of Table 9 below, it can beseen that the channel plan 2000D, which would require the use of S-CDMAfor all channels below 22.8 MHz, has a deployed upstream capacity ofjust over approximately 155 Mbits/s (corresponding to an effectiveupstream capacity of approximately 125 Mbits/s using an 80% de-ratingfactor):

TABLE 9 Channel BW Raw Data Rate Channel QAM (MHz) (Mbits/s) 32 (S-CDMA)3.2 12.8 32 (S-CDMA) 6.4 25.6 64 (S-CDMA) 6.4 30.72 64 6.4 30.72 64 6.430.72 64 3.2 15.36 16 3.2 10.24 TOTAL DEPLOYED CAPACITY 156.16

Although the proposed channel plan 2000C of FIG. 19 and proposed channelplan 2000D of FIG. 20, both employing multiple S-CDMA channels, promisedeployed upstream capacities on the order of 110 Mbits/sec and 155Mbits/sec, respectively, industry commentators have noted that suchplans have not been effectively adopted by operators of conventionalcable communication systems to achieve this degree of upstream capacity.In particular, while S-CDMA has been available since the advent ofDOCSIS version 2.0 in 2002, there has not been significant adoption ofS-CDMA technology by MSOs, in part due to some required improvements insoftware and algorithms employed by demodulation tuners of the CMTS todecode S-CDMA, and appropriate selection of spreading codes given thevariety of possible noise profiles that may be encountered in theupstream path bandwidth (e.g., see “Moto: S-CDMA Starting to Spread,”Jeff Baumgartner, Light Reading Cable, Feb. 16, 2010,http://www.lightreading.com/document.asp?doc_id=187997&site=lr_cable;also see Chapman, page 89).

Industry commentators also have noted that, even with S-CDMA and theadditional upstream channel bonding capabilities available with theadvent of DOCSIS version 3.0, at present the maximum effective upstreamcapacity arising from current implementations by some MSOs of upstreamchannel plans under DOCSIS version 3.0 is on the order just under 100Mbits/sec at best (e.g., see “Cisco Hints at What Comes After Docsis3.0,” Jeff Baumgartner, Light Reading Cable, May 14, 2012,http://www.lightreading.com/document.asp?doc_id=220896&site=lr_cable&).This arises from the channel plan 2000E shown in FIG. 21, which includesfour 64-QAM ATDMA channels 2002P each having a bandwidth of 6.4 MHz andhaving carrier frequencies of approximately 19.6 MHz, 26.0 MHz, 32.4MHz, and 38.8 MHz, respectively. In spite of the admonishments of HranacBroadband (i.e., placement of 64-QAM channels only below 30 MHz, andusing lower modulation order and lower bandwidth channels above 30 MHzto avoid undesirable diplex filter-related group delay effects), thechannel plan 2000E shown in FIG. 21 represents the presentmaximum-capacity state of the art for actual implementations of upstreamchannel plans by some MSOs. From FIG. 21 and Table 2, and with the aidof Table 10 below, it can be seen that the channel plan 2000E has adeployed upstream capacity of just over approximately 120 Mbits/s(corresponding to an effective upstream capacity of approximately 100Mbits/s using an 80% de-rating factor; see Chapman, page 8 and page 9,Table 1):

TABLE 10 Channel BW Raw Data Rate Channel QAM (MHz) (Mbits/s) 64 6.430.72 64 6.4 30.72 64 6.4 30.72 64 6.4 30.72 TOTAL DEPLOYED CAPACITY122.88

Some industry commentators have indicated that an effective upstreamcapacity of approximately 100 Mbits/s provided by the channel plan 2000Eof FIG. 21 is not so much a present reality as it is a near term target(e.g., see Chapman, pages 23 (Table 3), 63, and 138 regardingpresent-day maximum upstream capacity), at least in part due to ingressand other channel impairment issues discussed above (which arguablywould impact the full functionality of at least the lowest frequency“leftmost” channel and the highest frequency “rightmost” channel of theset of four channels 2002P).

Recent trends toward improving upstream capacity in a cablecommunication system relate to using more effective DOCSIS Physical(PHY) layer technologies (e.g., S-CDMA, see Chapman, pages 88 through95; Orthogonal Frequency Division Multiplexing or OFDM, see Chapman,pages 96 through 110), advanced error correction techniques (e.g., LowDensity Parity Check or LDPC codes, see Chapman, pages 119 through 121),decreasing node and/or service group size (e.g., decreasing the numberof subscriber premises per node and/or service group via node splittingor segmentation, see Chapman, pages 57 through 62), and expanding therange of frequencies allotted to the upstream path bandwidth (e.g., a“mid split” plan to expand the upstream path bandwidth to 85 MHz, a“high split” plan to expand the upstream path bandwidth to 200 MHz, anda “top-split” plan which would place additional upstream path bandwidthabove 1 GHz) (e.g., see Chapman, pages 10 through 21; also see Al-Banna,throughout). One proposed channel plan relating to a “mid split”upstream path bandwidth expansion suggests the use of seven 256-QAMATDMA 6.4 MHz bandwidth channels above 42 MHz (and no 256-QAM channelsin the “original” upstream path bandwidth from 5 MHz to 42 MHz) (e.g.,see Chapman, page 74, Table 17); this plan nonetheless requires S-CDMAchannels below 20 MHz (e.g., as seen in the channel plans 2000C and2000D of FIGS. 19 and 20, respectively).

Regarding proposals for expanding the range of frequencies allotted tothe upstream path bandwidth, some commentators have noted variouschallenges with such an expansion; for example, from a system componentsperspective, diplexers would need to be changed throughout the hardlinecable plant (such that the division between the upstream path bandwidthand the downstream path bandwidth would be moved to a higher portion ofthe spectrum), and active components as well as passive component mayneed to be retrofitted to accommodate higher frequency operation (see“HFC Network Capacity Expansion Options,” J. D. Salinger, The NCTA 2012Spring Technical Forum Proceedings, May 21, 2012, hereafter “Salinger,”which publication is hereby incorporated herein by reference in itsentirety). From an operational perspective, existing downstream analogchannels would need to be removed, which may not be possible for manyMSOs that are either required to maintain support for analog TVsdirectly, and/or are unable to remove analog channels for contractualreasons (Salinger, page 7). Even if removing analog channels ispossible, this option appears to require the installation of filters inmost or perhaps all subscriber premises equipment to both protect thenew portion of the spectrum from emissions by existing subscriberequipment, and to protect existing equipment from transmissions by newsubscriber premises equipment that would use the new portion ofspectrum.

SUMMARY

As discussed above, it is widely accepted in the cable communicationindustry that only a portion of the upstream path bandwidth generallyfrom about 20 MHz to 42 MHz may be used in some circumstances fortransmission of upstream information from subscriber premises to theheadend of the cable communication system via conventional accessprotocols such as time division multiple access (TDMA) or advanced timedivision multiple access (ATDMA). In tandem, it is also widely acceptedthat the lower portion of the upstream path bandwidth (e.g., generallyfrom about 5 MHz to about 20 MHz, and particularly below 18 MHz, andmore particularly below 16.4 MHz, and more particularly below 10 MHz) iseffectively unusable for conveying upstream information via TDMA orATDMA (e.g., see Chapman, pages 11, 69, 77, 88-89 and 128 (FIG. 53), and178 regarding usable/unusable spectrum).

It is also commonly presumed in the cable communication industry thategress serves as a proxy for ingress; i.e., where there is anopening/fault in the cable communication system that allows for signalleakage from the system to the outside (egress), such an opening/faultlikewise allows for unwanted outside signals to enter the cablecommunication system (ingress). Thus, prior conventional techniques forassessing ingress in a cable communication system have adopted testingequipment and protocols for detecting egress, and have presumed thatlocations in the system at which egress is detected correspond to faultsthat similarly allow for ingress into the system (and that repair ofsuch faults addresses ingress problems to the extent possible).

It is also commonly presumed in the cable communication industry that asignificant majority of cable communication system faults allowing foregress and ingress occur almost entirely in connection with systemelements associated with one or more subscriber premises. Morespecifically, subscriber service drops, and particularly subscriberpremises equipment (e.g., internal wiring, connectors, splitters,subscriber modem, etc.) are conventionally deemed to be the greatestsource (95% or greater) of egress and ingress problems in conventionalcable communication systems. Subscriber-related egress and ingressproblems generally are deemed to be especially difficult and in somecases impossible to adequately address, in that subscriber premisestypically are the least accessible, least controllable, and leastregularly-maintained elements of the cable communication system (i.e.,they are generally private residences or businesses that may bedifficult or impossible to access); furthermore, some significantsubscriber-related problems may be related to former subscribers, who nolonger receive services from the cable communication system operator,but may nonetheless still be physically connected to the system via asubscriber service drop and various system elements remaining in thepremises, any of which may have one or more faults. Moreover, withrespect to regular system maintenance, certain technicians typicallyresponsible for routine maintenance and repair of conventional cablecommunication systems arguably are the farthest removed from potentiallyaddressing such subscriber-related signal leakage problems.

More specifically, cable communication system operators (e.g., “MSOs”)typically maintain a staff of “maintenance technicians” (sometimes alsoreferred to as “line technicians”), and a separate staff of “fulfillmenttechnicians” (also sometimes referred to as “service technicians” or a“drop crew”). With reference again to FIGS. 1 and 2, maintenancetechnicians generally are responsible for maintaining and repairingconstituent elements of the RF hardline coaxial cable plant 180 ofrespective nodes 164A, 164B, 164C, etc., of the cable communicationsystem 160. One typical task performed by maintenance techniciansincludes a procedure referred to as a “sweep,” i.e., periodic testing ofa frequency response of the hardline cable plant 180, which may entailadjustment amplifiers 167 and laser power levels in RF/optical bridgeconverters 167 (in a node) and 175 (in the headend 162), or replacementof same and/or passive components in the node. Other examples of tasksthat may be performed by maintenance technicians from time to timeinclude egress testing (e.g., using commercially available egresstesting equipment) and occasionally ingress detection if a particularproblem is suspected with, or reported by, a given subscriber premises;as noted above, typical ingress detection involves the time consuming“divide and conquer” trial and error process of sequentiallydisconnecting respective sections of hardline coaxial cable 163B or“feeders” and concurrently monitoring resulting variations in the noiseprofile of the upstream path bandwidth. Maintenance technicianstypically do not attend to subscriber-related equipment or problems;generally speaking, the responsibility of maintenance technicians endsat the female connectors of the taps 188 to which subscriber servicedrops 163C are coupled (e.g., see FIG. 11, female connector 197B). Assuch, subscriber service drops and subscriber premises equipmenttypically are the least regularly-maintained portion of a conventionalcable communication system (i.e., there is typically no handling of thesubscriber service drops or access to subscriber premises equipment bythe cable communication system owner/operator's maintenancetechnicians).

Unlike maintenance technicians, fulfillment technicians (“servicetechnicians” or a “drop crew”) instead are generally responsible onlyfor attending to new subscriber services or subscriber serviceupgrades/downgrades (e.g., installation of a new subscriber service dropfrom a tap in the hardline cable plant, installation or removal ofvarious equipment and components inside a subscriber premisescorresponding to new service, upgraded service, or downgraded service,etc.). As such, fulfillment technicians are not involved with issuesrelating to the hardline cable plant or the headend, and very rarely, ifever, perform regular diagnostic, testing, maintenance or repair-relatedfunctions in connection with the overall cable communication system(fulfillment technicians typically are not qualified to, and in someinstances expressly forbidden from, working on the hardline coaxialcable plant or the headend).

For at least the foregoing reasons, the cable communication industry hasessentially resigned itself to the notions that: 1) most ingress is“subscriber-related” due to faults in subscriber service drops and/orsubscriber premises equipment, as well as ingress sources that are oftenrandom, intermittent, and/or impulse (broadband) in nature, originatefrom or local to subscriber premises, and generally challenging topinpoint; 2) as such, ingress is a virtually uncorrectable problem andcan be mitigated only to a limited extent (e.g., generally in the higherfrequency portion of the upstream path bandwidth above 20 MHz, usingegress testing as a proxy for detection of faults that may allow foringress); 3) as such, the portion of the upstream path bandwidth of acable communication system between 5 MHz and 20 MHz (and particularlybelow 18 MHz, and more particularly below 16.4 MHz, and moreparticularly below 10 MHz) is effectively unusable for conveyingupstream information from subscriber premises to the headend viaconventional TDMA and ATDMA protocols; and 4) to expand the upstreaminformation carrying capacity of cable communication systems, it will benecessary to: rely on advanced modulation techniques and/or signalingprotocols and error correction techniques that may be able to conveygreater amounts of information in the existing upstream path bandwidth;reduce node size and/or service group size; and/or establish new regionsof the electromagnetic spectrum in which upstream information may beconveyed (e.g., a “mid split” plan to expand the upstream path bandwidthto 85 MHz, a “high split” plan to expand the upstream path bandwidth to200 MHz, and a “top-split” plan which would place additional upstreampath bandwidth above 1 GHz).

In connection with the recommendations for expanding upstreaminformation carrying capacity noted in 4) immediately above, it isparticularly noteworthy that recent considerations in the industry havelargely ignored the infrastructure of the hardline cable plant itself asa possible source of improvement towards increased upstream capacity;instead, recent considerations have effectively deemed any conditioningof the outside plant unnecessary, and past attempts at ingressmitigation largely ineffective (see Chapman, pages 118-119 and FIG. 51).

In view of the conventional presumptions outlined above, the Inventorshave recognized and appreciated: 1) various shortcomings in the mannerin which the cable communication industry conventionally has approachedingress mitigation and has characterized limitations on the upstreampath bandwidth of a cable communication system due to ingress; and 2)various shortcomings in corresponding conventional approaches andproposals for future designs and implementations of cable communicationsystems.

For example, the Inventors have posited and verified that, contrary toconventional presumptions, egress is not a proxy for ingress.Accordingly, detecting and repairing system faults that allow for egressfrom a cable communication system does not necessarily identify oradequately address faults that may allow for ingress.

First, as noted above, egress is tested at aviation frequencies around120 MHz—i.e., at frequencies well above the presently-used upstream pathbandwidth from approximately 5 MHz to approximately 42 MHz (andaccordingly well beyond the frequency range in which ingress problematicto the upstream path bandwidth typically is encountered). Second, theInventors have appreciated that the presumption that egress is a proxyfor ingress fails to recognize that different types of faults in thecable communication system may form a wide variety of resonancestructures (and in some instances time-varying resonance structures)that may have a corresponding wide variety of frequency dependencies(and in some instances time-varying frequency dependencies). Stateddifferently, a particular fault forming a resonance structure that mayreadily allow signals having frequencies around 120 MHz to escape fromthe cable communication system as egress at a given point in time maynot necessarily allow for signals having significantly lower frequenciesto enter into the cable communication system as ingress (at the sametime or some later time). This situation may be particularly exacerbatedwhen comparing potential egress at around 120 MHz to potential ingressbelow 20 MHz (i.e., at frequencies typically corresponding toterrestrial signals including short wave radio signals).

The foregoing premise may be more readily appreciated by recognizing agiven fault in the cable communication system as an impairment (eitherstatic or dynamic) to a current path provided by conducting entities ofthe physical communication media carrying RF signals in the cablecommunication system. Such an impairment may arise, for example, from aloose, water-logged, oxidized or otherwise corroded connector and/or adamaged coaxial cable, and may be characterized as a resistor-capacitor(RC) or resistor-inductor-capacitor (RLC) circuit forming a resonancestructure whose frequency dependence may vary significantly (e.g., basedon representative values of resistance, capacitance and inductancecreated by the current path impairment). Furthermore, the nature of agiven impairment to the current path may in some instances change as afunction of time; for example, consider a loose connector, coupling asection of coaxial cable hanging on a utility pole to another systemcomponent, in the presence of significant wind and/or significanttemperature changes over some time period (the wind and/or temperaturechanges may dramatically change the nature of the impairment andcorresponding frequency response). Thus, a virtually unlimited varietyof such resonance structures may be created by respective faults in acable communication system, some of which may have a frequencydependence that allows for egress, and others of which may have asignificantly different frequency dependence that allows for ingress infrequency ranges particularly germane to the upstream path bandwidth.Accordingly, relying on egress as a proxy for ingress ignores a widevariety (and significant number) of frequency-dependent and/orfrequency-specific faults that may allow for ingress in the upstreampath bandwidth.

Furthermore, to the Inventors' knowledge, there has been no systematicapproach to date for verifying the presumption that a substantialportion of ingress in cable communication systems (i.e., approximately95% or greater) is “subscriber-related” (i.e., arising fromsubscriber-related signal leakage problems and/or ingress sourcesproximate to or within subscriber premises) and that, as a result,ingress is a virtually uncorrectable problem that can be mitigated onlyto a limited extent. More specifically, the Inventors have recognized ahistorical bias in the industry that placed significant attention onrandom, intermittent and/or bursty (impulse/broadband) ingress sourcesproximate to or within subscriber premises, and faults in subscriberservice drops or subscriber premises equipment that would readily admitingress from such sources.

In contrast, the Inventors have instead realized that greater attentionshould be given to more persistent narrowband ingress sources (“ingresscarriers”), such as terrestrial signals including short wave radiosignals, that are ubiquitously present in free space (i.e. notnecessarily subscriber-dependent sources), remain present in free spaceover generally longer periods of time (i.e., not necessarily bursty,random or intermittent), and can enter into the cable communicationsystem virtually anywhere within the RF footprint of the system(subscriber premises, subscriber service drops, and/or the hardlinecable plant).

With the foregoing in mind, the Inventors also have posited andverified, contrary to conventional presumptions, that the degree towhich the hardline cable plant itself may be responsible for ingress(presumed to be 5% or less) has been significantly underestimated by thecable communication industry, particularly with respect to narrowbandinterference signals as potential ingress sources. The conventionalpresumption that the hardline cable plant is responsible for onlyapproximately 5% of ingress corresponds to an approximately 0.2 dB ofpresumed potential impact on the noise profile of the upstream pathbandwidth; understandably, this is hardly an incentive for the industryto target the hardline cable plant, and as such there has been virtuallyno substantial focus in the industry on elements of the hardline coaxialcable plant (as opposed to subscriber service drops and/or subscriberpremises equipment) that may give rise to faults allowing for ingress.In particular, in spite of the various tasks typically performed bymaintenance or “line” technicians primarily responsible for the headendand hardline coaxial cable plant of a cable communication system, todate there has been no effective diagnostic testing in practicespecifically of the hardline cable plant to particularly identifyproblems in the plant itself that may be associated with ingress.

Moreover, as noted above, the limited conventional ingress detectionprocedures historically performed by maintenance technicians (e.g., a“divide and conquer” or “Ariadne's thread” approach involvingsequentially disconnecting respective sections of hardline coaxial cablein an attempt to identify a problem subscriber premises) are marginallyeffective at identifying some particular points of potential ingress(presumed to be subscriber-related), but essentially ignore thepossibility that persistent and ubiquitous terrestrial signals (as wellas other signals within the geographic area of the system and notnecessarily localized to a particular subscriber premises) couldconceivably enter into the system anywhere in the RF footprint.

With the foregoing in mind, the Inventors have approached the challengeof effective ingress mitigation in a cable communication system byrecognizing and underscoring the construct of a “neighborhood node,”i.e., the collection of the hardline coaxial cable plant, multiplesubscriber service drops, and corresponding multiple subscriber premisesthat are electrically connected to a common fiber optic cable andultimately coupled to a particular demodulation tuner port of a cablemodem termination system (CMTS). The construct and importance of aneighborhood node in connection with ingress mitigation methods,apparatus and systems according to various embodiments of the presentinvention is related at least in part to a phenomenon referred to as the“noise funneling affect,” and the Inventors appreciation of the role ofthe noise funneling effect particularly with respect to ingress.

FIG. 22 shows a portion of a neighborhood node 1640A so as toconceptually illustrate the “noise-funneling effect” associated withingress and other sources of noise (e.g., various system components) inthe node. In particular, FIG. 22 shows various elements of at least aportion of the hardline coaxial cable plant 180 in the neighborhood node1640A (e.g., hardline coaxial cable 163B, directional couplers 189,amplifiers 187, taps 188) distributed amongst multiple feeder branchesof the hardline coaxial cable plant that ultimately converge to anexpress feeder coupled to the optical/RF bridge converter 167. Ingressentering into various faults in the neighborhood node 1640A(conventionally presumed to be largely subscriber-related) is summedtogether as the ingress traverses different feeder branches of thehardline cable plant toward the headend 162; these different feederbranches are progressively joined together to reach the express feederand ultimately the neighborhood node's optical/RF bridge converter. Thenoise-summing process not only applies to ingress entering via one ormore faults in the neighborhood node, but also to sources of AdditiveWhite Gaussian Noise (AWGN) generated by various components of the node(e.g., subscriber premises equipment, amplifiers of the hardline coaxialcable plant) which collectively contribute to a “noise floor” of theneighborhood node pursuant to the noise-funneling effect.

The noise funneling effect illustrated in FIG. 22 dictates that: 1) oneor a small number of faults can cause the introduction of significantingress in the neighborhood node 1640A as observed at the headend 162(i.e., one “bad subscriber” may adversely affect the transmission ofupstream information from several/all subscriber premises on theneighborhood node); and 2) a noise power level due to ingress in thenode, as well as AWGN contributing to the noise floor of the node,generally increases as the number of subscriber premises in theneighborhood node increases. Stated differently, larger nodes (e.g., interms of one or more of households passed, number of subscribers, milestraversed, length of feeders, number of amplifiers, number of taps,etc.; see Table 1) generally are subject to higher levels of ingress anda higher noise floor. In terms of a node's cascade value N (NODE+N),nodes with higher values of N generally have higher levels of ingressand higher noise floors than nodes with lower values of N (the nodedepicted in FIG. 22 is illustrated as a relatively smaller node with acascade value of 2, i.e. NODE+2; however, as note above, typical cascadevalues of many conventional cable communication systems are NODE+5 orNODE+6) (see section 3.1, pages 3-4 of Al-Banna).

While the contribution of the hardline cable plant to noise in a givenneighborhood node is conventionally presumed to arise primarily fromvarious active components such as amplifiers (that produce AdditiveWhite Gaussian Noise), ingress on the other hand essentially has beenattributed exclusively to faults associated with subscriber servicedrops and subscriber premises. However, in contrast to this presumption,the Inventors have recognized and appreciated that a significant sourceof ingress arises from faults in the hardline cable plant itself Ingressresulting from such faults in the hardline cable plant itself travelsalong the hardline cable plant in a given neighborhood node toward theheadend and is additively funneled to a corresponding demodulation tunerport to which the neighborhood node is coupled. More specifically, theaccumulation of ingress from multiple faults particularly in thehardline coaxial cable plant (as well as subscriber-related faults) dueto the “noise-funneling” effect results in an appreciable presence ofbroadband noise and/or narrowband interference signals (“ingresscarriers”) in the lower portion of a spectrum of the upstream pathbandwidth in the neighborhood node, as observed at the headend (e.g.,via the analyzer 110 coupled to the RF splitter 173 shown in FIG. 4) oron the hardline cable plant (e.g., via the analyzer 110 coupled to thehardline cable plant 180 as shown in FIG. 2).

Thus, the Inventors have recognized and appreciated that the cablecommunication system as a whole, in terms of the conveyance of upstreaminformation from various subscriber premises in the system and noisethat could possibly interrupt or impede such conveyance of upstreaminformation, should be considered as a number of essentially independentneighborhood nodes, each of which is intended to function as its own“closed” sub-system. More specifically, each neighborhood node should beviewed as a closed communication sub-system, essentially isolated fromother neighborhood nodes of the overall system, in which the samefrequency spectrum assigned to the upstream path bandwidth anddownstream path bandwidth, respectively, may be re-used fromneighborhood node to neighborhood node. Accordingly, when one or moresuch neighborhood nodes are “breached” (e.g., particularly via faults inthe hardline coaxial cable plant of the neighborhood node), eachneighborhood node needs to be treated as its own sub-system in whichingress detection and remediation is warranted. To this end, theInventors have appreciated that all of the infrastructure within a givenneighborhood node (i.e., the hardline coaxial cable plant, in additionto the subscriber service drops and the subscriber premises) needs to beconsidered completely and holistically for any and all faults throughoutthe neighborhood node that could contribute in some manner to allowingfor ingress.

In view of the foregoing, various inventive embodiments disclosed hereinrelate to methods and apparatus for ingress mitigation in cablecommunication systems, and cable communication systems and methodshaving increased upstream capacity for supporting voice and/or dataservices based at least in part on such ingress mitigation. Variousaspects of such methods, apparatus and systems, in a manner contrary tothe conventional presumptions outlined above, involve some degree offocus on detecting and remediating faults particularly in the hardlinecoaxial cable plant of one or more neighborhood nodes of a cablecommunication system so as to significantly reduce ingress, andparticularly narrowband interference in the portion of the upstream pathbandwidth between approximately 5 MHz and approximately 20 MHz (in manyinstances arising from relatively persistent and non-localizedterrestrial signals such as short wave radio signals).

FIG. 23 is an illustration showing the concept of terrestrial signals3700 constituting a source of ingress and entering into one or morefaults 1800 in the hardline coaxial cable plant 180 of a cablecommunication system. As shown in FIG. 23, the propagation of someterrestrial signals depends in part on atmospheric conditions and thesolar cycle (increased solar activity causes ionization in the upperlayers of the atmosphere 4000, i.e., the “ionosphere”), which in turnaffects propagation of short wave signals). In any event, terrestrialsignals 3700 such as short wave radio signals are essentiallyubiquitous, in that their origin is not necessarily proximate to thecable communication system. Also, rather than manifest themselves asintermittent and/or random signals in the upstream bath bandwidth, theseterrestrial signals 3700 may constitute ingress sources over prolongedperiods of time whose presence in the upstream path bandwidth isrelatively persistent. As noted above, the Inventors have recognized andappreciated that the terrestrial signals 3700 can enter into the cablecommunication system virtually anywhere within the RF footprint of thesystem, particularly through one or more faults 1800 in the hardlinecoaxial cable plant 180 of one or more neighborhood nodes, and indeedcommonly constitute a significant manifestation of ingress in theportion of the upstream path bandwidth from approximately 5 MHz toapproximately 20 MHz (particularly below 18 MHz, more particularly below16.4 MHz, and more particularly below 10 MHz).

As discussed in greater detail below, pursuant to the Inventors'emphasis on the construct of neighborhood nodes, approaching the ingressmitigation challenge from the perspective of the hardline cable planttraversing a neighborhood node leads to significant, surprising, andunexpected results in terms of noise reduction in the upstream pathbandwidth, particularly below 20 MHz, via effective remediation offaults allowing for ingress (and particularly ingress due to relativelypersistent and non-localized terrestrial signals). In exemplaryimplementations according to various inventive embodiments disclosedherein, significant ingress mitigation in the portion of the upstreampath bandwidth of a given neighborhood node below approximately 20 MHz,particularly between 5 MHz and approximately 18 MHz, more particularlybetween 5 MHz and approximately 16.4 MHz, and more particularly between5 MHz and 10 MHz, has recovered bandwidth widely recognized aseffectively unusable to instead be more productively and reliablyemployed to facilitate increased upstream capacity for supporting voiceand/or data services.

In some exemplary embodiments of inventive ingress mitigation methodsaccording to the present invention, ingress mitigation may be approachedin two “phases” of activity. In a first phase (“phase 1”), variousinformation is collected from the field (e.g., proximate to the hardlinecable plant infrastructure and subscriber premises) to facilitateidentification of potential points of ingress in a given neighborhoodnode, with particular focus on one or more possible faults in thehardline coaxial cable plant that may allow for ingress. As part ofphase 1, information collected for this purpose may in someimplementations be visually rendered as a “neighborhood node ingressmap” to provide an intuitive illustration of ingress in the neighborhoodnode. In a second phase (“phase 2”), the information collected duringphase 1 (e.g., a neighborhood node ingress map) is used to facilitatemore particularly identifying specific faults in the field, remediatingsuch faults so as to significantly reduce ingress into the neighborhoodnode, and verifying the efficacy of fault remediation efforts toward areduction in ingress. In various implementations discussed in detailbelow, these respective phases of activity may be conducted by variouspersonnel assigned to multiple tasks involved in both phases ofactivity, or different personnel assigned to one or more tasks inrespective phases of activity at different times; in yet otherimplementations, various elements of phase 1 and phase 2 activity may becombined or merged into a unified process performed by one or morepersonnel. Thus, a wide variety of specific implementation options arecontemplated by the inventive concepts disclosed herein relating toingress mitigation.

In some exemplary embodiments of inventive ingress mitigation methodsaccording to the present invention, multiple different nodes of thecable communication system are treated separately and as their ownsub-system, and the complete infrastructure within a given neighborhoodnode (i.e., the hardline coaxial cable plant, in addition to thesubscriber service drops and the subscriber premises) is consideredholistically for possible faults throughout the node that may contributein some manner to allowing for ingress. To facilitate illustration ofsuch a holistic approach, FIG. 24 shows an example of a “cablefacilities map” for a neighborhood node of a cable communication node(the node shown in FIG. 24 is labeled as “BT-11”), and FIG. 25illustrates a zoomed-in portion of the cable facilities map shown inFIG. 24 (corresponding to the boxed-in area in the center portion of themap shown in FIG. 24). As used herein, the term “cable facilities map”(also sometimes referred to as a cable “plant map”) refers to a visualrepresentation of cable communication system infrastructure thatprovides a geographical framework for the respective locations of cablecommunication system components. In various examples of cable facilitiesmaps, subscriber service drops and subscriber premises may or may not beindicated; in particular, the illustrations shown in FIGS. 24 and 25only include infrastructure relating specifically to the hardlinecoaxial cable plant, and do not show any subscriber service drops orsubscriber premises.

As can be observed from FIGS. 24 and 25, cable communication systeminfrastructure within a given neighborhood node, and particularlyelements of the hardline coaxial cable plant deployed in a givenneighborhood node, often generally follow existing roadways in thegeographic area covered by the neighborhood node; in particular, thehardline coaxial cable plant may be deployed substantially or at leastpartially above ground on utility poles flanking and proximate toroadways (e.g., that provide access to subscriber premises), and/or inpart underground in trenches generally following a path proximate toroadways. Within a given neighborhood node, these roadways, and portionsof the hardline coaxial cable plant deployed proximate to such roadways,may sometimes pass through regions of the neighborhood node having arelatively lower density of premises (at least some of which may besubscriber premises), and at other points may pass through regions ofthe neighborhood node with a relatively higher density of premises (atleast some of which may be subscriber premises). In either case, as thehardline coaxial cable plant as well as the subscriber premises andassociated subscriber service drops may include one or more faults thatmay contribute in some manner to allowing for ingress, a “neighborhoodnode drive path” for a given neighborhood node is considered thataffords substantially full coverage of the neighborhood node.

With the foregoing in mind, in one embodiment of an ingress mitigationmethod according to the present invention, during a first phase ofactivity (“phase 1”) a mobile broadcast apparatus (e.g., which may besituated in a motorized or non-motorized vehicle, or carried/transportedby a technician on foot) equipped with a transmitter is driven orotherwise directed along a neighborhood node drive path proximate to theRF hardline coaxial cable plant of a neighborhood node, so as toeffectively traverse and ensure substantially full coverage of theneighborhood node. As the mobile broadcast apparatus is driven (orotherwise directed) along the neighborhood node drive path, one or moretest signals having one or more frequencies within the upstream pathbandwidth is/are broadcast from the transmitter at a plurality oflocations distributed along the drive path. Also as the mobile broadcastapparatus is driven (or otherwise directed) along the drive path,geographic information corresponding to respective positions of themobile broadcast apparatus along the drive path is electronicallyrecorded (e.g., via a navigational device such as a GPS apparatus, or a“smart” phone configured with navigational functionality) so as togenerate a first record of the geographic information (e.g., as afunction of time). At the same time, via an analyzer (e.g., a spectrumanalyzer or a tuned receiver) at the headend of the cable communicationsystem (or otherwise coupled to the hardline coaxial cable plant of theneighborhood node), a plurality of signal amplitudes at the test signalfrequency/frequencies are recorded so as to generate a second record;the plurality of signal amplitudes represent a strength of one or morereceived upstream test signals as a function of time, based on the testsignal(s) broadcast from the mobile broadcast apparatus as the mobilebroadcast apparatus traverses the drive path and test signal ingress ofthe test signal(s) into one or more faults in the hardline coaxial cableplant. In exemplary implementations, the generation of the first recordof geographic information is accomplished independently of thebroadcasting of the test signal(s) and the generation of the secondrecord of the plurality of signal amplitudes; i.e., the generation ofthe first record of geographic information corresponding to respectivepositions of the mobile broadcast apparatus along the drive path doesnot rely on the integrity of the transmitted test signal(s), nor does itrely on reliable reception of the test signal(s) at the headend of thecable communication system.

In one aspect of this embodiment, based on the first record ofgeographic information relating to the mobile broadcast apparatuspositions and the second record of signal amplitudes representing thestrength of received upstream test signals as a function of time, a“neighborhood node ingress map” may be generated. In one exemplaryimplementation, such a neighborhood node ingress map may include a firstgraphical representation of the neighborhood node drive path, and asecond graphical representation, overlaid on the first graphicalrepresentation, of the plurality of signal amplitudes so as toillustrate the test signal ingress of the test signal(s) into thehardline coaxial cable plant of the neighborhood node. In someimplementations discussed in greater detail below, the second graphicalrepresentation of the plurality of signal amplitudes may be in the formof a “heat map” (e.g., in which different signal amplitudes arerepresented by different colors) to provide an intuitive visualizationof the test signal ingress over the entire RF footprint of (and theoverall geographic area covered by) the neighborhood node.

More specifically, in another aspect, by traversing an entirety of theneighborhood node drive path, broadcasting the test signal(s) at aplurality of locations distributed along the entirety of the drive path,recording the geographic information corresponding to the respectivepositions of the mobile broadcast apparatus along the entirety of theneighborhood node drive path so as to generate the first record of thegeographic information, and recording the plurality of signal amplitudesat the test signal frequency/frequencies throughout traversing theentirety of the drive path so as to generate the second record, aneffectively complete picture of possible faults in the hardline coaxialcable plant and corresponding test signal ingress may be visuallyconveyed by the neighborhood node ingress map. To this end, in exemplaryimplementations, frequent, regular and/or periodic measurements aretaken (e.g., every second) of mobile broadcast apparatus position alongthe drive path; similarly, amplitude measurements corresponding to oneor more received upstream test signals are frequently, regularly and/orperiodically recorded by the analyzer (e.g., a spectrum analyzeroperating in a “free run” mode, or a tuned receiver having a relativelyhigh sampling rate). In one significant aspect, such amplitudemeasurements are recorded whether or not there is an appreciablepresence of one or more received upstream test signals at a given time,so as to obtain a comprehensive mobile broadcast apparatus position/testsignal ingress profile for the neighborhood node. Furthermore, since thetest signal(s) is/are broadcast at known times (e.g., eithercontinuously over a given time period, or periodically at known times asthe mobile broadcast apparatus traverses the drive path), theidentification of potential ingress points does not depend onpotentially intermittent, random and unpredictable signals generated byan actual ingress source. Thus, the approach adopted for phase 1activity significantly reduces the time and effort needed to identifypotential points of ingress in a cable communication system.

In yet another aspect, based at least in part on the presumption that insome instances a drive path for a given neighborhood node may involveone or more curvilinear portions (i.e., such that the drive path viewedas a whole may be referred to as a “curvilinear neighborhood node drivepath”), the first record of geographic information and the second recordof signal amplitudes representative of test signal ingress into thehardline coaxial cable plant (e.g., proximate to the drive path) may beprocessed so as to render an augmented data set representative of testsignal ingress across a two-dimensional geographic footprint of theneighborhood node. For example, in one implementation, the plurality ofsignal amplitudes in the second record, representing the strength of thereceived upstream test signal(s) as a function of time and along thedrive path, may be interpolated so as to provide estimated signalamplitudes for respective geographic positions within the neighborhoodnode beyond the drive path. In particular, the first record ofgeographic information representing mobile broadcast apparatus positionsalong the drive path may be expanded to include multiple additionalgeographic points distributed with some resolution across a substantialportion of the two-dimensional geographic footprint of the neighborhoodnode (e.g., in some cases at substantial distances from the drive path),and for each such additional geographic point a corresponding estimatedsignal amplitude may be generated based on interpolation of signalamplitudes contained in the second record.

Accordingly, in some embodiments a neighborhood node ingress map may begenerated based at least in part on such expanded/interpolated data.Such a neighborhood node ingress map provides an enhanced intuitivevisual aid for identifying potential points of ingress in theneighborhood node based on respective and cumulative contributions toingress from multiple possible faults in the hardline coaxial cableplant (as well as subscriber-related faults in subscriber service dropsand/or subscriber premises equipment). As discussed in greater detailbelow, other types of information processing and/or visualrepresentations of “raw” or processed information relating to mobilebroadcast apparatus position and signal amplitudes of one or morereceived upstream test signals, and/or selection of one or more testsignal frequencies for the one or more test signals broadcast from themobile broadcast apparatus, may further facilitate: 1) determination ofspecific types and/or locations of faults in the hardline coaxial cableplant; 2) differentiation of faults in the hardline coaxial cable plantfrom subscriber-related faults; and/or 3) prioritization of multiplehardline plant-related and/or subscriber-related faults (e.g.,determination of a relative “severity” of multiple faults) so as to inturn facilitate appropriate and efficient fault remediation and ingressmitigation efforts.

As noted above, the information collected during phase 1 (e.g., aneighborhood node ingress map) may be used in methods according to otherembodiments of the invention relating to a second phase of activity(“phase 2”), relating at least in part to particularly identifyingspecific faults in the field, remediating such faults so as tosignificantly reduce ingress in the neighborhood node, and/or verifyingthe efficacy of fault remediation efforts toward a reduction in ingress.In particular, in some exemplary implementations, one or more faults inthe hardline coaxial cable plant of a given neighborhood node arespecifically identified and remediated so as to significantly reduce anoise power (e.g., as measured at the headend of the cable communicationsystem) associated with the neighborhood node ingress in at least aportion of the upstream path bandwidth below approximately 20 MHz (e.g.,particularly below approximately 18 MHz, and more particularly belowapproximately 16.4 MHz, and more particularly below approximately 10MHz). Examples of faults in the hardline coaxial cable plant that may beremediated (e.g., via repair or replacement of a defective component) soas to significantly reduce a noise power associated with neighborhoodnode ingress include, but are not limited to, one or more loose and/ordefective connectors (loose/defective “fittings”), one or more flaws inthe hardline coaxial cable, and a compromised ground (e.g., compromisedRF shielding) or other defect in one or more electronics components(e.g., amplifiers, directional couplers, taps, line terminators) of thehardline coaxial cable plant.

More specifically, in some implementations, one or more faults in thehardline coaxial cable plant of a given neighborhood node may berepaired or replaced such that a highest value for an average noisepower in at least a portion of the upstream path bandwidth belowapproximately 20 MHz (e.g., as measured over at least a 24 hour periodat the headend) is less than approximately 20 decibels (dB) (and moreparticularly less than 15 dB, and more particularly less than 10 dB, andmore particularly less than 8 dB) above a noise floor associated withthe upstream path bandwidth below 20 MHz (e.g., as measured at theheadend over the same time period). In other implementations, one ormore faults in the hardline coaxial cable plant may be repaired orreplaced such that a highest value for the average noise power in atleast a portion of the upstream path bandwidth below approximately 20MHz (e.g., as measured over at least a 24 hour period at the headend) isat least 22 decibels (dB) (and more particularly at least 24 dB, andmore particularly at least 27 dB, and more particularly at least 30 dB,and more particularly at least 33 dB, and more particularly at least 36dB, and more particularly at least 38 dB) below an average channel powerof one or more physical communication channels having a carrierfrequency in the portion of the upstream path bandwidth belowapproximately 20 MHz and carrying upstream information from one or moresubscriber premises in the neighborhood node.

In yet other implementations, one or more faults in the hardline coaxialcable plant may be repaired or replaced so as to achieve acarrier-to-noise-plus-interference ratio (CNIR) of at least 25 decibels(dB) (and more particularly at least 28 dB, and more particularly atleast 31 dB, and more particularly at least 34 dB, and more particularlyat least 37 dB) associated with one or more physical communicationchannels deployed in the upstream path bandwidth of the neighborhoodnode (and, more specifically, channels deployed in a portion of theupstream path bandwidth below approximately 19.6 MHz, and moreparticularly below approximately 18 MHz, and more particularly belowapproximately 16.4 MHz, and more particularly below approximately 10MHz). In yet other implementations, one or more faults in the hardlinecoaxial cable plant may be repaired or replaced so as to achieve anunequalized modulation error ratio (MER) of at least 17 decibels (dB)(and more particularly at least 20 dB, and more particularly at least 22dB, and more particularly at least 24 dB, and more particularly at least28 dB, and more particularly at least 30 dB) associated with one or morephysical communication channels deployed in the upstream path bandwidthof the neighborhood node (and, more specifically, channels deployed in aportion of the upstream path bandwidth below approximately 19.6 MHz, andmore particularly below approximately 18 MHz, and more particularlybelow approximately 16.4 MHz, and more particularly below approximately10 MHz). In yet other implementations, one or more faults in thehardline coaxial cable plant may be repaired or replaced so as tosignificantly reduce a noise power (e.g., as measured at the headend)associated with one or more narrowband substantially persistent ingresssignals (e.g., short wave radio signals) constituting at least part ofthe neighborhood node ingress. Again, these results are significant,unexpected, and surprising, particularly given the cable communicationindustry's previously undisputed presumption that the portion of theupstream path bandwidth below approximately 20 MHz purportedly suffersfrom an irreparable presence of ingress.

In other embodiments of ingress mitigation methods, an iterativeapproach is adopted in which identification of potential points ofingress in a given neighborhood node and corresponding remediation ofhardline plant-related and/or subscriber-related faults are conductedsuccessively and multiple times to document a progression of ingressmitigation efforts in a given neighborhood node (e.g., in someimplementations, the various noise metrics and communication channelmetrics discussed above may be achieved via multiple iterations of“phase 1” and “phase 2” activity). More specifically, the Inventors haverecognized and appreciated that: 1) as faults allowing for moresignificant ingress are remediated, “lesser” faults that allow forrelatively lower (but nonetheless potentially problematic) levels ofingress may become more evident during iterative phase 1 and phase 2activity; and 2) some faults may be intermittent (e.g., time-dependentand/or weather-dependent), and may be identifiable only via iterativephase 1 and phase 2 activity (e.g., over different time periods and/orweather conditions, and/or using different test signal frequencies) toidentify potential points of ingress.

In view of the foregoing, in one embodiment, after collection ofinformation during a first iteration of phase 1 activity in a givenneighborhood node (i.e. via broadcasting of one or more test signalsfrom a mobile broadcast apparatus traversing a neighborhood node drivepath and recording geographical information representing positions ofthe mobile broadcast apparatus along the drive path and signalamplitudes representing a strength of one or more received upstream testsignals based on the broadcasted test signal(s) and test signalingress), and after a first iteration of phase 2 activity in theneighborhood node (i.e., a first remediation of one or more hardlineplant-related and/or subscriber-related faults based on the firstiteration of phase 1 activity), an ingress mitigation method comprisesconducting at least a second iteration of phase 1 activity in theneighborhood node.

In one example implementation of this embodiment, a neighborhood nodeingress map is generated as part of the first iteration of phase 1activity, and a second iteration of the neighborhood node ingress map isgenerated as part of the second iteration of the phase 1 activity, so asto ascertain an effectiveness of the first remediation. In anotheraspect, the neighborhood node ingress map and the second iteration ofthe neighborhood node ingress map may be generated as an electronicvisual rendering having a plurality of independently selectable andindependently viewable layers comprising a first layer corresponding tothe neighborhood node ingress map and a second layer corresponding tothe second iteration of the neighborhood node ingress map, so as tofacilitate comparative viewing of the respective layers. In yet anotheraspect, a second iteration of phase 2 activity is conducted in theneighborhood node (a second remediation of one or more additionalhardline plant-related and/or subscriber-related faults based on thesecond iteration of phase 1 activity) and, after the second remediation,the ingress mitigation method comprises conducting at least a thirditeration of phase 1 activity in the neighborhood node. In yet anotheraspect, a third iteration of the neighborhood node ingress map isgenerated pursuant to the third iteration of phase 1 activity so as toprovide a time series of at least three neighborhood node ingress maps.

The cumulative effect of the iterative approach as outlined above, inwhich various components of the hardline coaxial cable plant and/orsubscriber service drops or subscriber premises equipment aresuccessively repaired or replaced, leads to a dramatic reduction ofingress in a given neighborhood node across the upstream path bandwidth,with a particularly noteworthy reduction in narrowband interference inthe portion of the upstream path bandwidth between approximately 5 MHzand approximately 20 MHz (and particularly between 5 MHz toapproximately 18 MHz, and more particularly between 5 MHz andapproximately 16.4 MHz, and more particularly between 5 MHz andapproximately 10 MHz). In some implementations, even a single iterationof phase 1 activity and phase 2 activity (in various possible modes ofexecution) results in a significant reduction of ingress in a givenneighborhood node. Thus, ingress mitigation methods according to variousembodiments of the present invention effectively recover valuablebandwidth, widely recognized as being otherwise effectively unusable, toinstead be more productively and reliably employed to facilitateincreased upstream capacity for supporting voice and/or data services.

More generally, pursuant to various inventive ingress mitigation methodsand apparatus disclosed herein, improved cable communication systems andmethods according to other embodiments of the present invention may berealized that previously were not possible. In particular, existingcable communication systems may be modified (e.g., repaired and/orupdated with new components) pursuant to the ingress mitigation methodsand apparatus disclosed herein to yield significantly improved cablecommunication systems according to various embodiments of the presentinvention. Similarly, new cable communication systems according tovarious embodiments of the present invention may be deployed in which,as part of a quality assessment of the newly installed system forexample, the ingress mitigation methods and apparatus disclosed hereinmay be applied to ascertain that various noise metrics are met toaccommodate significant increases in aggregate deployed upstreamcapacity as compared to conventional cable communication systems, and togenerally ensure reliable operation of the newly installed system. Forboth pre-existing and newly installed cable communication systems,ingress mitigation methods and apparatus according to variousembodiments of the present invention may be employed as part of aperiodic (e.g., routine or occasional) cable communication systemmaintenance program to ensure ongoing reliability of such increasedupstream capacity systems.

Furthermore, the Inventors have recognized and appreciated that adramatic reduction of ingress in a given neighborhood node, particularlybelow approximately 20 MHz, also may provide for greater effectivenessof ingress cancellation circuitry employed in some cable modemtermination system (CMTS) demodulation tuners, and/or obviate the needin some instances for advanced access protocols such as Synchronous CodeDivision Multiple Access (S-CDMA), thereby permitting expanded use ofTDMA/ATDMA channels in a previously unusable portion of the upstreampath bandwidth.

In particular, as noted above, ingress cancellation circuitry generallyis not effective below 20 MHz, where channels are most vulnerable tobroadband impulse noise and multiple significant ingress carriers (e.g.,see Chapman, page 69; also see Thompson, pages 148-149, “LaboratoryMeasurements”). Instead, for this lower portion of the upstream pathbandwidth, the industry has proposed the use of S-CDMA, which has apurported increased resistance to broadband impulse noise. However,while the spreading code employed in S-CDMA to significantly expandsymbol duration purportedly renders this protocol somewhat moreresistant to demodulation/decoding errors due to the presence ofbroadband noise in the upstream path bandwidth, S-CDMA is arguablysignificantly less effective in the presence of narrowband and/orpersistent interference signals or “ingress carriers” (e.g., due to hamradio and/or short wave terrestrial signals), which may be present fordurations in excess of the expanded time per symbol. Accordingly, thepurported benefits of S-CDMA may be most realized in portions of theupstream path bandwidth susceptible to broadband burst/impulse noise butin which there is only a modest presence at most of narrowbandinterference (where ingress cancellation circuitry similarly may beeffective, i.e., above 20 MHz). In view of the foregoing, with referenceagain to the proposed channel plans 2000C and 2000D illustrated in FIGS.19 and 20, respectively, the S-CDMA channels below approximately 20 MHzarguably would not function effectively due to the presence of ingressdisturbances typically encountered in this region of the upstream pathbandwidth (e.g., as discussed above in connection with FIGS. 12, 14 and15). In fact, as discussed above, industry adoption of S-CDMA as asolution for implementing channels below 20 MHz has been notablylimited, and S-CDMA remains largely unused in practice by cable systemoperators (e.g., see Chapman, page 89).

Thus, given the limited efficacy of conventional ingress cancellationcircuitry, and arguably limited efficacy (and limited adoption) ofS-CDMA, cable communication systems according to various embodiments ofthe present invention having significantly reduced noise in the upstreampath bandwidth of respective neighborhood nodes enable improvedperformance of ingress cancellation circuitry below 20 MHz (e.g., bysignificantly reducing troublesome ingress carriers that impedesatisfactory functioning of ingress cancellation circuitry), and alsoenable an expanded use of commonly implemented TDMA/ATDMA channels below20 MHz to increase upstream capacity for supporting voice and/or dataservices. Furthermore, such reduced noise cable communication systemsenable the implementation of upstream QAM channels with highermodulation orders (and hence increased deployed channel data rates)throughout the upstream path bandwidth from approximately 5 MHz to atleast approximately 42 MHz as compared to conventional cablecommunication systems (even in the absence of forward error correction,adaptive equalization and/or ingress cancellation), thus providingsignificantly increased aggregate deployed upstream capacity in a givenneighborhood node. When reduced noise cable communication systemsaccording to various embodiments of the present invention are coupledwith one or more of adaptive equalization and ingress cancellation forphysical communication channels, forward error correction (e.g.,Reed-Solomon FEC or LDPC—see Table 6 above), and optionally advancedprotocols such as S-CDMA or Orthogonal Frequency Division Multiplexing(OFDM), even further enhancements in aggregate deployed upstreamcapacity may be realized in the upstream path bandwidth of respectiveneighborhood nodes of the system (e.g., using QAM channels havingmodulation orders in excess of 256).

To provide an illustration of exemplary aggregate deployed upstreamcapacity gains facilitated by various embodiments of the presentinvention, FIG. 26 is a chart similar to that shown in FIGS. 17 through21, in which incremental aggregate deployed upstream capacity gains maybe observed via the use of higher modulation order QAM channels indifferent portions of the upstream path bandwidth in a givenneighborhood node. In FIG. 26, the channel plan 2002P shown in FIG. 21(i.e., including four 64-QAM 6.4 MHz-wide channels occupying a portionof the upstream path bandwidth between 16.4 MHz and 42 MHz andrepresenting the current “state-of-the-art” in some conventional cablecommunication systems in active use) is represented as providingapproximately 123 Mbits/s of maximum aggregate deployed upstreamcapacity between 16.4 MHz and 42 MHz (see Table 10). In one embodimentof a cable communication system according to the present invention, thefour 64-QAM channels of the channel plan 2002P shown in FIG. 21 may bereplaced by four 256-QAM channels, providing an aggregate deployedupstream capacity gain of approximately 41 Mbits/s (for a total of123+41=164 Mbits/s). While not shown explicitly in FIG. 26, it may beappreciated that in other embodiments, the four 64-QAM channels of thechannel plan 2002P alternatively may be replaced by four 128-QAMchannels, or a combination of 128-QAM and 256-QAM channels, to providesome incremental gain in aggregate deployed upstream capacity beyond 123Mbits/s.

In another embodiment, whether or not 64-QAM or higher modulation orderQAM channels are employed above 16.4 MHz, as illustrated in FIG. 26three or more 16-QAM channels (e.g., TDMA or ATDMA channels) may beadded in the portion of the upstream path bandwidth from approximately5.2 MHz to approximately 16.4 MHz based on channel bandwidths havingmultiples of 1.6 MHz (e.g., one 1.6 MHz-wide channel, one 3.2 MHz-widechannel, and one 6.4 MHz-wide channel, or other combinations of 1.6MHz-wide and/or 3.2 MHz-wide channels) to provide an aggregate deployedupstream capacity gain of approximately 36 Mbits/s. In yet anotherembodiment, these 16-QAM channels may be replaced by 64-QAM channels toprovide approximately another 18 Mbits/s gain in aggregate deployedupstream capacity and, in yet another embodiment, these 64-QAM channelsmay be replaced by 256-QAM channels to provide approximately another 18Mbits/s gain in aggregate deployed upstream capacity (i.e., total gainin aggregate deployed upstream capacity by using 256-QAM channelsbetween approximately 5.2 MHz and approximately 16.4 MHz isapproximately 72 Mbits/s).

While not shown explicitly in FIG. 26, different incremental gains inaggregate deployed upstream capacity may be obtained in otherembodiments by using 32-QAM or 128-QAM channels between approximately5.0 MHz and approximately 16.4 MHz, and various combinations of QAMchannels having different modulation orders and/or bandwidths (includingchannel bandwidths smaller than 1.6 MHz, so as to further fill theportion of the upstream path bandwidth between 5.0 MHz and 5.2 MHz). Inany event, by using QAM channels having a modulation order as high as256 throughout the upstream path bandwidth from approximately 5.2 MHz toapproximately 42 MHz in a given neighborhood node of a cablecommunication system according to one embodiment of the presentinvention, a total aggregate deployed upstream capacity of approximately240 Mbits/s may be realized—almost doubling the aggregate deployedupstream capacity of “state-of-the-art” conventional cable communicationsystems.

Furthermore, while FIG. 26 illustrates an example of aggregate deployedupstream capacity in a cable communication system according to oneembodiment of the present invention, enabled at least in part by ingressmitigation methods, apparatus and systems according to other embodimentsof the present invention, it should be appreciated that the invention isnot limited to the upstream capacity improvements shown in FIG. 26. Inparticular, in other embodiments, cable communication systems may berealized in which the noise profile of a given neighborhood node (e.g.,the noise floor arising from AWGN, and other disturbances/interferencecombined therewith) over a substantial portion of the upstream pathbandwidth from approximately 5 MHz to at least approximately 42 MHzallows for C/N values that, when combined with advanced error correctiontechniques such as LDPC, support functioning QAM channels havingmodulation orders in excess of 256 (e.g., see Table 6, in which a C/Nvalue of 34 dB supports 4096-QAM using LDPC ⅚ error correction). In thismanner, aggregate deployed upstream capacities of up to approximately350 Mbits/s may be achieved in cable communication systems according tovarious embodiments of the present invention (e.g., using 4096-QAMchannels having a deployed data rate of 9.6 Mbits/s/MHz across theupstream path bandwidth from approximately 5 MHz to at leastapproximately 42 MHz; see Table 3).

In sum, one embodiment of the present invention is directed to a methodfor facilitating detection of potential points of signal ingress in acable communication system. The method comprises: A) broadcasting a testsignal in an upstream path bandwidth of the cable communication systemfrom a plurality of locations proximate to at least one node of thecable communication system; B) recording corresponding geographicinformation for the plurality of locations, at respective ones of theplurality of locations, together with a first plurality of correspondingtime stamps, so as to generate a first record of the geographicinformation for the plurality of locations at which the test signal isbroadcast in A) as a function of time; C) recording, at a headend of thecable communication system, a plurality of signal amplitudes togetherwith a second plurality of corresponding time stamps so as to generate asecond record, the plurality of signal amplitudes representing astrength of a received upstream test signal at the headend as a functionof time, based on A); and D) based on the first record and the secondrecord, generating an ingress map including a graphical representationof the potential points of signal ingress in the at least one node ofthe cable communication system.

Another embodiment is directed to a system for detecting potentialpoints of signal ingress in a cable communication system. The systemcomprises: A) a mobile broadcast apparatus to broadcast a test signal inan upstream path bandwidth of the cable communication system from aplurality of locations proximate to at least one node of the cablecommunication system; B) a navigational device, coupled to the mobilebroadcast apparatus, to record corresponding geographic information forthe plurality of locations, at respective ones of the plurality oflocations, together with a first plurality of corresponding time stamps,so as to generate a first record of the geographic information for theplurality of locations at which the test signal is broadcast by themobile broadcast apparatus as a function of time; C) a signal receiverto record, at a headend of the cable communication system, a pluralityof signal amplitudes together with a second plurality of correspondingtime stamps so as to generate a second record, the plurality of signalamplitudes representing a strength of a received upstream test signal atthe headend as a function of time, based on the test signal transmittedby the mobile broadcast apparatus; and D) at least one processor toprocess the first record and the second record so as to generate aningress map including a graphical representation of the potential pointsof signal ingress in the at least one node of the cable communicationsystem based on the first record and the second record.

Another embodiment is directed to a method for facilitating detection ofpotential points of signal ingress in a cable communication system. Themethod comprises: A) broadcasting, from a signal generator coupled to orsituated in a vehicle, a test signal in an upstream path bandwidth of atleast one node of the cable communication system; B) during A),operating the vehicle so as to traverse a plurality of locationsproximate to the at least one node of the cable communication system;and C) recording, using a navigational device coupled to or situated inthe vehicle, corresponding geographic information for the plurality oflocations, at respective ones of the plurality of locations, togetherwith a first plurality of corresponding time stamps, so as to generate afirst record of the geographic information for the plurality oflocations at which the test signal is broadcast in A) as a function oftime, wherein in A): the test signal does not significantly interferewith operative signaling in the upstream path bandwidth from one or moreend users on the at least one node of the cable communication system;and the test signal does not include the geographic information for theplurality of locations recorded in C).

Another embodiment is directed to a computer-implemented method forfacilitating detection of potential points of signal ingress in a cablecommunication system. The method comprises: A) receiving or accessing afirst electronic record including: geographic information for aplurality of locations at which a test signal is broadcast in anupstream path bandwidth of at least one node of the cable communicationsystem, the plurality of locations being proximate to the at least onenode of the cable communication system; and a first plurality ofcorresponding time stamps, such that the first record includes thegeographic information for the plurality of locations at which the testsignal is broadcast as a function of time; B) receiving or accessing asecond electronic record including: a plurality of signal amplitudesrecorded at a headend of the cable communication system, the pluralityof signal amplitudes representing a strength of a received upstream testsignal at the headend based on the broadcasted test signal; and a secondplurality of corresponding time stamps, such that the second recordincludes the plurality of signal amplitudes as a function of time; C)merging the first electronic record and the second electronic record,based at least in part on the first plurality of corresponding timestamps and the second plurality of corresponding time stamps, so as togenerate a third electronic record including at least the geographicinformation for the plurality of locations at which the test signal isbroadcast and the plurality of signal amplitudes representing thestrength of the received upstream test signal; and D) processing thethird electronic record so as to generate an ingress map including agraphical representation of the potential points of signal ingress inthe at least one node of the cable communication system.

Another embodiment is directed to a method for reducing or remediatingsignal ingress in at least one node of a cable communication system. Themethod comprises: A) transmitting a local test signal, at or proximateto at least one potential point of the signal ingress, in an upstreampath bandwidth of the at least one node of the cable communicationsystem; B) receiving, at or proximate to the at least one potentialpoint of the signal ingress, at least one signal amplitude representinga strength of a received upstream test signal at a headend of the cablecommunication system, based on A); C) based at least in part on the atleast one signal amplitude received in B), identifying, at or proximateto the at least one potential point of the signal ingress, at least onefaulty or defective infrastructure element of the at least one node ofthe cable communication system; and D) repairing or replacing the atleast one faulty or defective infrastructure element so as to reduce orremediate the signal ingress.

Another embodiment is directed to an apparatus for facilitatingdetection of signal ingress in at least one node of a cablecommunication system. The apparatus comprises: at least one antenna; atransmitter, coupled to the at least one antenna, to transmit a localtest signal via the at least one antenna in an upstream path bandwidthof the at least one node of the cable communication system; at least onecommunication interface to receive signal information relating to atleast one signal amplitude representing a strength of a receivedupstream test signal at a headend of the cable communication system,based on the local test signal transmitted by the transmitter; and atleast one display device, coupled to the at least one communicationinterface, to display at least one indication, based at least in part onthe received signal information, corresponding to the at least onesignal amplitude representing the strength of the received upstream testsignal at the headend of the cable communication system.

Another embodiment is directed to an apparatus for facilitatingdetection of signal ingress in at least one node of a cablecommunication system. The apparatus comprises: at least one antenna; atransmitter, coupled to the at least one antenna, to transmit a localtest signal via the at least one antenna in an upstream path bandwidthof the at least one node of the cable communication system withoutsignificantly interfering with operative signaling in the upstream pathbandwidth from one or more end users on the at least one node of thecable communication system; at least one communication interface toreceive at least signal information relating to at least one signalamplitude representing a strength of a received upstream test signal ata headend of the cable communication system, based on the local testsignal transmitted by the transmitter; at least one display device; atleast one memory to store: processor-executable instructions; first mapinformation relating to an ingress map illustrating a plurality ofpotential points of the signal ingress and corresponding signalamplitudes indicating relative degrees of the signal ingress, atrespective ones of the plurality of potential points, in a geographicarea proximate to the at least one node of the cable communicationsystem; and second map information relating to at least a portion of acable communication system facilities map illustrating at least aportion of an infrastructure of the at least one node of the cablecommunication system; at least one processor, communicatively coupled toat least the at least one memory, the at least one display device, andthe at least one communication interface; and a portable or handheldhousing for at least the transmitter, the at least one communicationinterface, the at least one display device, the at least one memory, andthe at least one processor, wherein upon execution of theprocessor-executable instructions, the at least one processor: controlsthe at least one display device to display an ingress overlay mapcomprising the ingress map and at least the portion of the cablecommunication system facilities map overlaid on the ingress map; andfurther controls the at least one display device to display at least oneindication, based at least in part on the signal information received bythe at least one communication interface, corresponding to the at leastone signal amplitude representing the strength of the received upstreamtest signal at the headend of the cable communication system.

Further combinations and sub-combinations of various concepts areprovided below in the Detailed Description and Claims. It should beappreciated that all combinations of the foregoing concepts andadditional concepts discussed in greater detail below (provided suchconcepts are not mutually inconsistent) are contemplated as being partof the inventive subject matter disclosed herein. In particular, allcombinations of subject matter appearing as numbered claims at the endof this disclosure are contemplated as being part of the inventivesubject matter disclosed herein. In addition, all combinations ofsubject matter supported by this disclosure, including the drawings, thedescription and the claims, are contemplated as being part of theinventive subject matter even if not expressly recited as one of thenumbered claims. It should also be appreciated that terminologyexplicitly employed herein that also may appear in any disclosureincorporated by reference should be accorded a meaning most consistentwith the particular concepts disclosed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

The patent or application file contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawing(s) will be provided by the Office upon request and paymentof the necessary fee.

The skilled artisan will understand that the drawings primarily are forillustrative purposes and are not intended to limit the scope of theinventive subject matter described herein. The drawings are notnecessarily to scale; in some instances, various aspects of theinventive subject matter disclosed herein may be shown exaggerated orenlarged in the drawings to facilitate an understanding of differentfeatures. In the drawings, like reference characters generally refer tolike features (e.g., functionally similar and/or structurally similarelements).

FIG. 1 illustrates various aspects of a conventional cable communicationsystem.

FIG. 2 illustrates various details of a hardline coaxial cable plant andan example subscriber premises of the cable communication system shownin FIG. 1.

FIGS. 3A through 3G illustrate various components of the hardlinecoaxial cable plant shown in FIG. 2.

FIG. 4 illustrates various aspects of a headend of the cablecommunication system shown in FIG. 1.

FIG. 5 is a graph illustrating a plot of quadrature amplitude modulation(QAM) signal amplitude and phase in terms of in-phase and quadraturecomponents to facilitate an understanding of information transmissionvia QAM signals in a cable communication system similar to that shown inFIG. 1.

FIG. 6 illustrates a constellation diagram for quadrature phase shiftkeyed (QPSK) (i.e., 4-QAM) modulation that may be employed fortransmission of information in a cable communication system similar tothat shown in FIG. 1.

FIG. 7 illustrates a constellation diagram for 16-QAM that may beemployed for transmission of information in a cable communication systemsimilar to that shown in FIG. 1.

FIG. 8 illustrates a constellation diagram for 64-QAM that may beemployed for transmission of information in a cable communication systemsimilar to that shown in FIG. 1.

FIG. 9 illustrates a constellation diagram for 256-QAM that may beemployed for transmission of information in a cable communication systemsimilar to that shown in FIG. 1.

FIG. 10 illustrates a bar graph showing different modulation orders forQAM, different bandwidths for communication channels over whichinformation is transported via QAM RF signals, and corresponding maximumdeployed (or “raw”) data rates for the channels.

FIG. 11 illustrates a portion of the hardline coaxial cable plant, anddetails of a subscriber premises coupled to the hardline coaxial cableplant of the cable communication system shown in FIG. 1.

FIG. 12 shows an example of a power spectral density (PSD) (or“spectrum”) associated with an upstream path bandwidth in a conventionalcable communication system similar to that shown in FIG. 1, so as toillustrate the presence of ingress.

FIG. 13 shows another example of a spectrum associated with the upstreampath bandwidth of a conventional cable communication system similar tothat shown in FIG. 1, so as to illustrate the presence of ingress in theform of broadband impulse noise.

FIG. 14 shows yet another example of a spectrum associated with theupstream path bandwidth of a conventional cable communication systemsimilar to that shown in FIG. 1, so as to illustrate the presence ofingress.

FIG. 15 shows the spectrum of FIG. 14 and two hypothetical channelspositioned over a significantly noisy portion of the spectrum toillustrate the concept of carrier-to-interference noise.

FIG. 16 illustrates the effect of noise on the demodulation of QAMsignals using an example of a QPSK or 4-QAM constellation diagram.

FIG. 17 illustrates a chart showing a typical DOCSIS upstream channelplan for a conventional cable communication system, with two channelsplaced between 20 MHz and 42 MHz.

FIG. 18 illustrates a chart showing a proposed DOCSIS upstream channelplan for a conventional cable communication system, with five channelsplaced between 20 MHz and 42 MHz.

FIG. 19 illustrates a chart showing another proposed DOCSIS upstreamchannel plan for a conventional cable communication system, includingtwo proposed channels placed below 20 MHz and requiring Synchronous CodeDivision Multiple Access (S-CDMA).

FIG. 20 illustrates a chart showing yet another proposed DOCSIS upstreamchannel plan for a conventional cable communication system, includingthree proposed channels placed below 20 MHz and requiring SynchronousCode Division Multiple Access (S-CDMA).

FIG. 21 illustrates a chart showing a DOCSIS upstream channel plan for aconventional cable communication system, including four 64-QAM AdvancedTime Division Multiple Access (ATDMA) channels occupying the upperportion of the upstream path bandwidth of a neighborhood node.

FIG. 22 shows various components of a node of the cable communicationsystem of FIG. 1 so as to illustrate the “noise funneling effect.”

FIG. 23 is an illustration showing the concept of terrestrial signalsconstituting a source of ingress and entering into one or more faults inthe hardline coaxial cable plant of a cable communication system.

FIG. 24 illustrates a cable facilities map for a neighborhood node of acable communication system according to one embodiment of the presentinvention.

FIG. 25 illustrates a portion of the cable facilities map of FIG. 24 toshow additional details of cable communication system infrastructure ina portion of the neighborhood node.

FIG. 26 illustrates a chart similar to that shown in FIGS. 17 through21, in which incremental upstream capacity gains may be observed via thedeployment of higher modulation order QAM channels in different portionsof the upstream path bandwidth in one or more neighborhood nodes ofcable communication systems according to various embodiments of thepresent invention.

FIG. 27 is an illustration similar to FIG. 1 showing a cablecommunication system according to one embodiment of the presentinvention, in which ingress mitigation methods and apparatus accordingto various embodiments were employed and in which the efficacy of suchmethods and apparatus was demonstrated.

FIG. 28 illustrates a functional block diagram of an ingress detectionsystem, according to one embodiment of the present invention, foraccurately and efficiently identifying points of signal ingress in acable communication system and facilitating remediation of same.

FIG. 29 illustrates a flow chart of a method for facilitating ingressdetection and mapping, according to one embodiment of the presentinvention.

FIG. 30 illustrates variations in received test signal amplitude asmonitored by the analyzer shown in FIG. 28, based on a distance betweena fault in a cable communication system and a transmitter transmittingthe test signal, according to one embodiment of the present invention.

FIG. 31 illustrates an interference pattern model, according to oneembodiment of the present invention, of test signal ingress via tworelatively widely-separated faults in a cable communication system.

FIG. 32 illustrates an interference pattern model, according to oneembodiment of the present invention, of test signal ingress via tworelatively narrowly-separated faults in a cable communication system.

FIGS. 33 through 36 illustrate examples of neighborhood node ingressmaps in the form of two-dimensional “heat maps,” in which a visual coderepresenting ingress is implemented as a color code, according to oneembodiment of the present invention.

FIG. 37 illustrates a heat map similar to the map shown in FIG. 33, onwhich are indicated potential points of signal ingress, according to oneembodiment of the present invention.

FIG. 38 illustrates another example of a neighborhood node ingress mapin the form of a modified topographical map (e.g., contour map),according to one embodiment of the present invention.

FIG. 39 illustrates another example of a neighborhood node ingress mapin the form of a one-dimensional map (e.g., plot on a graph of signalamplitudes as a function of distance), according to one embodiment ofthe present invention.

FIG. 40 illustrates another example of a neighborhood node ingress mapin the form of a three-dimensional map, according to one embodiment ofthe present invention.

FIG. 41 illustrates another example of a neighborhood node ingress mapin the form of an ingress overlay map, in which the heat map of FIG. 33is overlaid on the cable facilities map of FIG. 24, according to oneembodiment of the present invention.

FIG. 42 illustrates a portion of the ingress overlay map of FIG. 41 toshow additional details of cable communication system infrastructure anda possible hardline coaxial cable plant-related fault in a portion ofthe neighborhood node.

FIG. 43 illustrates a parcel map corresponding to the neighborhood nodeshown in FIGS. 41 and 42.

FIG. 44 illustrates another example of a neighborhood node ingress mapin the form of an ingress overlay map, in which the heat map of FIG. 33is overlaid on the parcel map of FIG. 43, according to one embodiment ofthe present invention.

FIG. 45 illustrates a portion of the ingress overlay map of FIG. 44.

FIG. 46 illustrates another example of a neighborhood node ingress mapin the form of an ingress overlay map, in which the heat map of FIG. 33is overlaid on an aerial image, according to one embodiment of thepresent invention.

FIG. 47 illustrates a portion of the ingress overlay map of FIG. 46.

FIG. 48 illustrates a flow chart of a method for ingress detection andremediation according to one embodiment of the present invention.

FIGS. 49A through 49L illustrate expanded close-up views of facilitiesmaps showing cable communication system infrastructure, correspondingheat maps before ingress remediation, and corresponding heat maps afteringress remediation, according to embodiments of the present invention.

FIG. 50 illustrates a spectrum of the upstream path bandwidth of aneighborhood node selected for ingress mitigation according to thepresent invention, in which a test channel is transmitting, prior toingress mitigation and corresponding to the heat map of FIG. 33.

FIG. 51 illustrates a spectrum of the same upstream path bandwidthmonitored in FIG. 50, after a first iteration of ingress remediation andcorresponding to the heat map of FIG. 34.

FIG. 52 illustrates a spectrum of the same upstream path bandwidthmonitored in FIGS. 50 and 51, after a second iteration of ingressremediation and corresponding to the heat map of FIG. 35.

FIG. 53 illustrates a spectrum of the same upstream path bandwidthmonitored in FIGS. 50, 51, and 52, after a third iteration of ingressremediation and corresponding to the heat map of FIG. 36.

FIG. 54 illustrates a comparison of a first spectrum representing a 24hour average noise power in the neighborhood node for which spectra areshown in FIGS. 50-53, prior to ingress mitigation according to thepresent invention, and a second spectrum representing a 24 hour averagenoise power in the same neighborhood node following ingress mitigation.

FIG. 55 illustrates a three-dimensional graph showing a first timeseries of hourly spectra of the upstream path bandwidth of the sameneighborhood node over a 24 hour period, prior to ingress mitigationaccording to the present invention.

FIG. 56 illustrates a three-dimensional graph showing a second timeseries of hourly spectra of the upstream path bandwidth of the sameneighborhood node over a 24 hour period, following ingress mitigationaccording to the present invention.

FIGS. 57 through 60 are graphs illustrating unequalized and equalizedmodulation error ratio (MER) of the test channel shown in the spectra ofFIGS. 50 through 53, respectively, as a function of packets received,after each iteration of ingress remediation.

FIGS. 61A and 61B represent pre-ingress mitigation and post-ingressmitigation constellation diagrams, respectively for the test channelshown in FIGS. 50 through 53.

FIG. 62 shows a screen-shot of a QAM analyzer, illustrating apost-ingress mitigation constellation diagram and graph of unequalizedMER as a function of packets received, for a 16-QAM ATDMA test channelhaving a carrier frequency of 16.4 MHz and employed in the neighborhoodnode for which spectra are shown in FIGS. 50-53, to verify the efficacyof ingress mitigation methods, apparatus and systems according tovarious embodiments of the present invention.

FIG. 63A shows the constellation diagram from the screen-shot of FIG.62, and FIGS. 63B, 63C, 63D and 63E show similar constellation diagramsfor 16-QAM ATMDA test channels used respectively in four other controlnodes of the cable communication system, in which control nodes ingressmitigation was not performed according to the present invention, so asto provide a comparative illustration of the efficacy of ingressmitigation methods, apparatus and systems according to variousembodiments of the present invention.

DETAILED DESCRIPTION

Following below are more detailed descriptions of various conceptsrelated to, and embodiments of, inventive methods and apparatus foringress mitigation in cable communication systems, and cablecommunication systems and methods having increased upstream capacity forsupporting voice and/or data services. It should be appreciated thatvarious concepts introduced above and discussed in greater detail belowmay be implemented in any of numerous ways, as the disclosed conceptsare not limited to any particular manner of implementation. Examples ofspecific implementations and applications are provided primarily forillustrative purposes.

I. SYSTEM OVERVIEW TO DEMONSTRATE EFFICACY

To demonstrate the various concepts disclosed herein, ingress mitigationmethods and apparatus according to embodiments of the present inventionwere employed in a functioning cable communication system similar tothat shown in FIGS. 1 through 4, having multiple neighborhood nodesrespectively serving numerous subscriber premises. Noise profiles of theupstream path bandwidth in multiple different neighborhood nodes of thiscable communication system first were studied so as to collect generalbaseline information (e.g., 24 hour average spectrums for the upstreampath bandwidth were acquired for each of the neighborhood nodes toobtain representative noise power spectrums), and one neighborhood nodewith a noteworthy noise profile showing a significant presence ofingress particularly between 5 MHz and 20 MHz was chosen in which toimplement ingress mitigation methods as outlined in greater detail below(this neighborhood node is referred to herein as the “ingress mitigatednode”). Four other nodes of the cable communication system, alldemonstrating appreciable ingress, served as “control nodes” in which noingress mitigation was performed, so as to provide a system-widecomparative basis for illustrating the efficacy of the ingressmitigation methodology.

As noted above, in some exemplary embodiments of inventive ingressmitigation methods according to the present invention, ingressmitigation may be approached in two “phases” of activity. In a firstphase (“phase 1”), various information is collected from the field(e.g., proximate to the hardline cable plant infrastructure andsubscriber premises) to facilitate identification of potential points ofingress into a given neighborhood node under evaluation, with particularfocus on one or more possible faults in the hardline coaxial cable plantthat may allow for ingress. As part of phase 1, information collectedfor this purpose may in some implementations be visually rendered as a“neighborhood node ingress map” to provide an intuitive illustration ofingress in the neighborhood node. In a second phase (“phase 2”), theinformation collected during phase 1 (e.g., a neighborhood node ingressmap) is used to facilitate particularly identifying specific faults inthe field, remediating such faults so as to significantly reduce ingressinto the neighborhood node, and verifying the efficacy of faultremediation efforts toward a reduction in ingress.

Accordingly, as part of the ingress mitigation methodology employed inthe ingress mitigated node, multiple potential points of ingress in theingress mitigated node initially were identified during phase 1activity, and based on such identification multiple and iterativeremediation efforts in the ingress mitigated node were performed (e.g.,repair and/or replacement of various components), particularly inconnection with the RF hardline coaxial cable plant of the node, duringphase 2 activity. With each iteration of remediation, measurements weremade including a noise power spectrum of the upstream path bandwidth inthe ingress mitigated node so as to illustrate incremental reductions iningress; additionally, measurements were made of a carrier-to-noiseratio (CNR) and a modulation error ratio (MER) (unequalized andequalized) of a quadrature amplitude modulation (QAM) radio frequency(RF) signal defining a physical communication test channel in thelower-frequency portion of the upstream path bandwidth of the ingressmitigated node (e.g., carrier frequency of 16.4 MHz) and carryingsimulated upstream information, so as to illustrate correspondingimprovements in the upstream information carrying capacity of theupstream test channel.

After a series of remediation efforts, a 24 hour average noise powerspectrum of the ingress mitigated node was measured, so as to provide a“before and after” illustration of the dramatic reduction of noise powerin the ingress mitigated node throughout the upstream path bandwidthfrom approximately 5 MHz to at least approximately 42 MHz (e.g., on theorder of at least a 6 dB reduction throughout the spectrum, and in someinstances as much as a 14 dB reduction particularly below 20 MHz, andmore particularly below 18 MHz, and more particularly below 16.4 MHz,and more particularly below 10 MHz). Post-mitigation free run spectrafor the ingress mitigated node revealed an essentially Additive WhiteGaussian Noise (AWGN) noise floor profile from approximately 5 MHz to atleast approximately 42 MHz, with essentially no presence of discreteingress carriers.

Similarly, CNR and MER values for the upstream test channel after eachiteration of remediation, and particularly after a series of remediationefforts, illustrated a dramatic improvement in channel metrics andperformance (e.g., CNR as high as approximately 40 to 44 dB—see Table 4;unequalized MER as high as approximately 30 dB and equalized MER as highas approximately 40 dB—see Table 5). Observed CNR and MER values werestable and sufficient to support significantly higher QAM modulationorders (e.g., up to at least 256-QAM) and corresponding increasedupstream capacity throughout the upstream path bandwidth (e.g., at leastup to approximately 240 Mbits/s of aggregate deployed upstream capacitybetween approximately 5 MHz to approximately 42 MHz), using aconventional Advanced Time Division Multiple Access (ATDMA) accessprotocol and without necessarily requiring advanced error correctiontechniques (e.g., Low Density Parity Check or LDPC codes), a SynchronousCode Division Multiple Access (S-CDMA) protocol, or Orthogonal FrequencyDivision Multiplexing (OFDM) (although one or more of LDPC, S-CDMA, andOFDM may be employed in cable communication systems according to variousembodiments of the present invention, as discussed further below).

FIG. 24 illustrates part of a cable facilities map 310 that includes theingress mitigated node, labeled in the map as node “BT-11”. FIG. 25illustrates a portion 310A of the cable facilities map 310 to showadditional details of cable communication system infrastructure in partof the ingress mitigated node corresponding to the portion 310A of thecable facilities map 310 (in which portion some exemplary remediationwas performed, as discussed in greater detail below). In particular,with reference again to FIG. 2, as can be seen in FIG. 25 the portion310A of the cable facilities map 310 indicates multiple segments ofhardline coaxial cable 163B (in which different segments may employdifferent diameters of hardline coaxial cable), a number of amplifiers187 (indicated by a triangular-shaped symbol, and including one or moreexamples of a “gainmaker” multi-port amplifier), a number of taps 188(e.g., including two-port taps indicated by a circle enclosing a tapattenuation value in dB, and four-port taps indicated by a squareenclosing a tap attenuation value in dB), a number of directionalcouplers 189 (indicated by a half-filled circle), a number of lineterminators 191, and a number of splice blocks 195, in the correspondingportion of the ingress mitigated node.

Table 11 below is similar to Table 1 discussed above, and providesvarious parameters relating to the architecture and infrastructure ofthe ingress mitigated node BT-11 shown in FIGS. 24 and 25. As comparedto the parameters listed in Table 1 representative of a generic“typical” neighborhood node (e.g., see Chapman, pages 35-47 and 57-62),as can be seen from Table 11 ingress mitigated node BT-11 includes fewerhouseholds passed (HHP) and subscriber premises than the typical noderepresented in Table 1, but has a significantly higher mileage andcascade, and includes a significantly greater number of amplifiers thandoes the typical node represented in Table 1. Accordingly, regardingarchitectural and infrastructure parameters that significantly bear uponthe noise profile of a given neighborhood node (particularly inconsideration of the “noise funneling effect” discussed above inconnection with FIG. 12), BT-11 provides a wholly suitable example of aworking neighborhood node of a cable communication system providingongoing services to a plurality of subscribers and in which the efficacyof ingress mitigation methods and apparatus according to the presentinvention may be clearly demonstrated.

TABLE 11 INGRESS MITIGATED NODE BT-11 Households Passed (HHP) 285Subscriber Premises (e.g., high speed data) 40% (114) HHP Density 27HHP/mile Node Mileage 10.566 miles Cascade NODE + 8 Amplifiers/Mile4.54/mile Taps/Mile 17.32/mile Amplifiers  48 Taps 183 Highest Tap Value23 dB Lowest Tap Value 4 dB Express Feeder Cable Type 0.875 & 0.725 inchPIII Largest Express Feeder Span 2314 feet Feeder (distribution) CableType 0.625 & 0.500 inch PIII Feeder Cable Distance to First Tap ~200feet Largest Feeder Span 1388 feet Subscriber Drop Cable Type Series 6Largest Drop Cable Span 200 feet Maximum Subscriber Modem Transmit Power55 dBmV

In the ingress mitigated node BT-11, the subscriber premises constituteda service group sharing a QPSK upstream physical communication channelhaving a carrier frequency of approximately 25 MHz and a channelbandwidth of 3.2 MHz. The channel utilization index of the upstreamchannel was at least 50% or greater, and on the order of approximately70% during peak usage periods.

As part of the test methodology to demonstrate the efficacy of ingressmitigation on the ingress mitigated node BT-11, a test modem wasdeployed in the neighborhood node to transmit QAM RF signals having acarrier frequency of 16.4 MHz and carrying test information representingadditional upstream information (“simulated upstream traffic”) from atheoretical additional service group of subscriber premises in the node.FIG. 27 is an illustration similar to FIG. 1 showing a cablecommunication system 160A according to one embodiment of the presentinvention, in which the neighborhood node 164A represents the ingressmitigated node BT-11 shown in FIG. 24, and in which an exemplary testmodem 1065 is shown coupled to the hardline coaxial cable plant 180 ofthe ingress mitigated node BT-11, in addition to the subscriber modems165 forming the service group 195. The test modem 1065 was mounted on autility pole in a protective housing, together with a wireless routercoupled to the test modem (to provide a controllable source of testinformation for transmission as additional simulated upstream traffic).The test modem 1065 was coupled to a corresponding subscriber servicedrop, which drop in turn was coupled to an available port of a tap inthe hardline cable plant. The wireless router was in communication witha server at the headend 162, which server was running a script to pollthe router at its designated IP address to continually request therouter's configuration set-up webpage (including various .html and .jpegcontent), which served as the additional simulated upstream traffic.

A given QAM RF signal transmitted by a test modem 1065 defined aphysical communication test channel 2103T in the upstream path bandwidth182 of the ingress mitigated node; in various tests, a channel bandwidthof 3.2 MHz, and QAM modulation orders of 4 (QPSK) and 16, respectivelywere employed for the QAM RF signals transmitted by test modem 1065 andconstituting the test channel 2103T. From empirical observations oftransmission bursts of the test channel 2103T in free-run spectrumsdisplayed by a spectrum analyzer serving as the analyzer 110 at theheadend 162, the additional simulated upstream traffic constituted achannel utilization index for the test channel 2103T on the order ofapproximately 20% to 30%. Examples of modems employed for test modemsrepresented in FIG. 27 by the test modem 1065, as well as subscribermodems 165 in the ingress mitigated node BT-11 (and modems used in otherneighborhood nodes of the cable communication system 160A) include theMotorola Surfboard series (e.g., Motorola SB 4200, 5101, 5120, SBG 900),Ambit models U100018 and U100019, and Arris models 502G, 602G and 652Gmedia terminal adaptors. The CMTS 170 at the headend 162 of the cablecommunication system 160A was a Cisco 7200 series VXR running DOCSISversion 1.1, and both the test modems and the CMTS 170 implemented ReedSolomon Forward Error Correction (FEC), pre-equalization/adaptiveequalization, and Advanced Time Division Multiple Access (ATDMA) for thetest channels.

With respect to other elements of infrastructure not specificallyindicated in Table 11 above, in the cable communication system 160Ashown in FIG. 27 the RF/optical bridge converter 167 in the ingressmitigated node BT-11 and the RF/optical bridge converter 175 at theheadend 162 were ADC Homeworx ISX 3040 converters with 1310 nanometeroptics. FIG. 27 also illustrates that, in addition to the analyzer 110coupled to the RF splitter 173 at the headend 162, a QAM analysis deviceconstituting test and/or monitoring equipment 256 (also see FIG. 4) wascoupled to the RF splitter 173 to provide one or more of CNR values,unequalized and equalized MER values, and constellation diagrams forreceived and demodulated QAM RF signals corresponding to test channelsexemplified by the test channel 2103T. In the various tests performed,an HP 8591C or an Agilent n9000A spectrum analyzer was employed for theanalyzer 110, and the JDSU PathTrack™ HCU-200 Integrated Return PathMonitoring Module (e.g., seehttp://www.jdsu.com/ProductLiterature/hcu200_ds_cab_tm_ae.pdf) wasemployed as the test and/or monitoring equipment 256 used for variousmeasurements of channel metrics reported herein.

II. INGRESS MITIGATION SYSTEMS AND APPARATUS

FIG. 28 illustrates a functional block diagram of an ingress detectionsystem 100, according to one embodiment of the present invention, foraccurately and efficiently identifying points of signal ingress in acable communication system and facilitating remediation of same (again,the efficacy of the system 100 was demonstrated in a functioning cablecommunication system as discussed above).

In various aspects, the ingress detection system 100 includes one ormore instrumentation components and/or computing devices (e.g., one ormore computers, portable/handheld computing devices, etc.), and utilizesa communications infrastructure (which at least in part may employnetwork elements and/or dedicated communication links, components,devices, etc.) to provide communication of information amongstrespective components/devices of the system and various parties fromwhich relevant information may be acquired and/or to which informationmay be provided. While FIG. 28 illustrates a number of systemcomponents/devices and parties that may exchange information with eachother as part of implementing the ingress detection system 100, itshould be appreciated that not all of the components/devices/partiesshown in FIG. 28 are necessarily required to implement the variousembodiments discussed herein of ingress detection systems, andassociated methods and apparatus. In particular, in various embodiments,some or all of the components/devices shown in FIG. 28, in a variety ofcombinations, may be employed to realize a particular implementation ofan ingress detection system, and various ingress detection andmitigation methods, according to the present invention.

In general, as shown in FIG. 28 the ingress detection system 100 mayinclude, but is not limited to, an analyzer 110 (e.g., a spectrumanalyzer or a tuned receiver disposed in the headend 162 of a cablecommunication system), test and/or monitoring equipment 256 (e.g., a QAManalysis device, also disposed in the headend 162), a processor 120, amobile broadcast apparatus 130, a portable or handheld field device 140(used by a field technician) and a communication network 150. The system100 is implemented in connection with a cable communication system(e.g., similar to the cable communication system 160 shown in FIG. 1 orthe cable communication system 160A shown in FIG. 27). For purposes ofillustration, FIG. 28 shows a portion of one neighborhood node 164Acoupled to the headend 162 of such a cable communication system,including various elements of the neighborhood node as depicted in FIGS.1, 2 and 25 (e.g., fiber optic cable 163A, optical/RF bridge converter167, RF hardline coaxial cable plant 180, hardline coaxial cable 163B,subscriber service drops 163C, subscriber premises 190, test modem1065). FIG. 28 also illustrates a portion of a neighborhood node drivepath 305 (e.g., labeled in FIG. 28 as “Elm St.” and “Oak St.”),proximate to the hardline coaxial cable plant 180, along which themobile broadcast apparatus 130 is driven so as to effectively traverseand ensure substantially full coverage of the neighborhood node 164A.

In the system 100 shown in FIG. 28, communication network 150 providesfor communication between two or more components/devices relating to theingress detection system 100. For example, network 150 provides thecommunication infrastructure by which information may be exchangedbetween any two or more of the mobile broadcast apparatus 130, portableor handheld field device 140, processor 120, the analyzer 110, and thetest and/or monitoring equipment 256. Communication network 150 may be,for example, any local area network (LAN) and/or wide area network (WAN)for connecting to the Internet. Communication network 150 also may beimplemented at least in part by a wired/wireless telecommunicationsnetwork, and/or may facilitate radio communication (e.g., two-way radiotransmission via personal communication devices).

As shown in FIG. 28, respective components/devices of the ingressdetection system 100 may include one or more communication interfaces tofacilitate communication of various information. For example, acommunication interface 138 of mobile broadcast apparatus 130, acommunication interface 142 of portable or handheld field device 140, acommunication interface 122 of processor 120, and a communicationinterface 112 of analyzer 110 may be employed to provide connectivity toother components/devices of the system 100 (e.g., via communicationnetwork 150) (the test and/or monitoring equipment 256 similarly mayinclude such a communication interface). Communication interfaces 112,122, 138 and 142 may be any wired and/or wireless communicationinterfaces by which information may be exchanged between anycomponents/devices of the ingress detection system 100. Example wiredcommunication interfaces may include, but are not limited to, USB ports,RS232 connectors, RJ45 connectors, and Ethernet connectors. Examplewireless communication interfaces may include, but are not limited to,Bluetooth technology, Wi-Fi, Wi-Max, IEEE 802.11 technology, radiofrequency (RF), LAN, WAN, Internet, shared wireless access protocol(SWAP), Infrared Data Association (IrDA) compatible protocols and othertypes of wireless networking protocols, and any combinations thereof.

As also shown in FIG. 28, one or more components/devices of ingressdetection system 100 generally include a memory (e.g., one or morecomputer-readable storage media) to store processor-executableinstructions as well as other data (e.g., see memory 116, 126, 136 and146), and a display device to facilitate display of various information(e.g., see example display devices 111, 121, 145; while not explicitlyshown in FIG. 28, any of the components/devices constituting the system100 may include a display device). One or more components/devices alsomay include one or more processing units (e.g., a microprocessor,microcontroller, CPU, FPGA, etc.; see example processing units 114, 124,134 and 144) communicatively coupled to the communication interface andthe memory, wherein upon execution of the processor-executableinstructions by the processing unit, the processing unit performs avariety of functions as set forth in greater detail below for respectivecomponents/devices. Generally speaking, many of the functionalitiesdescribed herein and attributed to various components/devices of, or incommunication with, the ingress detection system 100 shown in FIG. 28may be encoded as processor-executable instructions stored in/on one ormore computer-readable storage media. Similarly, while not shownexplicitly for all components/devices of the ingress detection system100, any one or more such components/devices may include a userinterface to facilitate control and/or exchange of information between auser/technician (e.g., the technicians 118 or 148) and thecomponent/device.

Although some aspects of various embodiments may take advantage of oneor more wireless communication networks (e.g., at least a portion of thecommunication network 150) to afford real-time or near real-timerelaying, processing, and display of various information relating toingress detection and remediation, such communication networks are notrequired for the successful operation of the system 100. For example,due to a lack of wireless coverage in some particular area or afinancially driven decision to forgo additional wireless data expenses,there may be situations in which real-time communications are notavailable. In such cases the various components of the system 100 may beused to transmit, receive, record, store, and/or process variousinformation for further use/processing at a later time, which may bemerely when cellular connectivity is again available (e.g., a techniciantravels back into an area with cellular coverage), or at the end of ashift when a technician might transfer field-collected data to theprocessor 120 (i.e., via Wi-Fi, Ethernet, memory card, thumb drive,etc.). Specifically, the headend-based equipment (e.g., the analyzer 110and/or test/monitoring equipment 256) may measure and record variousinformation, while field-based equipment separately may record variousinformation (e.g., transmit location, bearing, pitch, roll, transmiton/off status, ambient noise/ingress, etc.), which may at a later timebe combined via automated (e.g., restored wireless communicationconnection) and/or manual (transfer of information to the processor 120via a portable memory device) techniques.

Similarly, historical data may be loaded onto a field device (e.g., themobile broadcast apparatus 130 or the portable/handheld field device140) so that it is viewable in a field location where no wirelesscommunication service may be available. Visualizations of such data,discussed in greater detail below, may include a time line that may bemanipulated for reviewing data non-linearly, or replaying the data inconjunction with a technician's current position to simulate an originalwalk-through/drive-through of the neighborhood node or a portion thereofbased on geographic position and signal amplitude information (first andsecond information records, as discussed in greater detail below).

A. Mobile Broadcast Apparatus

The mobile broadcast apparatus 130, employed during phase 1 ingressdetection activity (discussed in detail further below in connection withFIG. 29), may include one or more processing units (CPU) 134, one ormore communication interfaces 138, memory 136, a transmitter 135, anantenna 131, and a navigation device 132. The electronics portion of themobile broadcast apparatus may be implemented in various form factors,examples of which include, but are not limited to, computing ortelecommunications devices such as a portable computer, tablet device, apersonal digital assistant (PDA), smart phone, cellular radio telephone,mobile computing device, touch-screen device, touchpad device, orgenerally any device including, or connected to, a processor and displaydevice.

Navigational device 132 is co-located with the mobile broadcastapparatus 130 and reliably records the geographical position of themobile broadcast apparatus in the field as a function of time (e.g., thenavigational device logs, as a “first record,” geographic coordinatessuch as GPS coordinates, together with a time stamp). Examples ofnavigational devices include, but are not limited to, conventionaldedicated GPS devices or telecommunication devices (e.g., “smart”phones) configured with navigational functionality. The navigationaldevice 132 may include a global positioning system (GPS) receiver or aglobal navigation satellite system (GNSS) receiver; in one aspect, sucha receiver may provide a data stream formatted as a National MarineElectronics Association (NMEA) data stream. In one exemplaryimplementation, the navigational device may include an ISM300F2-C5-V0005GPS module available from Inventek Systems, LLC of Westford, Mass. (seewww.inventeksys.com/html/ism300f2-c5-v0005.html). The Inventek GPSmodule includes two UARTs (universal asynchronous receiver/transmitter)for communication with a processor, supports both the SIRF Binary andNMEA-0183 protocols (depending on firmware selection), and has aninformation update rate of 5 Hz. A variety of geographic locationinformation may be requested from and provided by the navigationaldevice 132 including, but not limited to, time (coordinated universaltime—UTC), date, latitude, north/south indicator, longitude, east/westindicator, number and identification of satellites used in the positionsolution, number and identification of GPS satellites in view and theirelevation, azimuth and SNR values, and dilution of precision values.Accordingly, it should be appreciated that in some implementations thenavigational device 132 may provide a wide variety of geographicinformation as well as timing information (e.g., one or more timestamps).

In another exemplary implementation, the navigational device may includean HTC EVO mobile telecommunication device (seehttp://www.htc.com/us/products/evo-sprint) running the Ride Loggerapplication (seehttp://www.appbrain.com/app/ride-logger/com.nickholliday.ridelogger),which captures the following fields: time, longitude, latitude, speed(mph), distance (miles), averageSpeed (mph), bearing, accuracy,satellites, altitude (feed), and acceleration (g).

In one embodiment, as shown in FIG. 28, mobile broadcast apparatus 130may comprise, be coupled to or situated in, a vehicle 133. In variousimplementations, the vehicle may be a motorized vehicle (e.g., car,truck, motorized cart, all-terrain/off-road vehicle, etc.) or analternatively-powered vehicle (e.g., a bicycle). The type of vehicleemployed in connection with the mobile broadcast apparatus 130 maydepend at least in part on various aspects of the terrain generally in agiven neighborhood node, and more specifically the nature of theneighborhood node drive path over which the vehicle traverses (e.g.,paved, unpaved, readily accessible, partially obstructed, etc.), whichin turn may depend at least in part on the topography of the geographicarea particularly traversed by the hardline coaxial cable plant (towhich the neighborhood node drive path generally remains proximate). Insome embodiments, the mobile broadcast apparatus 130 may becarried/transported by a person on foot (e.g., in a backpack), or by aperson pushing, pulling or otherwise operating a non-motorized vehicleor motorized vehicle.

In one example, the transmitter 135 may be a CB radio, for broadcastinga test signal at one or more frequencies falling within an upstream pathbandwidth of the node(s) (e.g., 5 MHz to at least 42 MHz). In oneparticular implementation, the transmitter 135 is configured to transmitthe test signal having a test signal frequency of approximately 27 MHz;however, as discussed further below, it should be appreciated that avariety of test signal frequencies are contemplated according to variousembodiments. Also, the test signal may be broadcast at various powerlevels, depending in part on one or more of the transmitter design, thefrequency or frequencies at which the test signal is transmitted, anyapplicable regulatory guidelines that may apply regarding transmissionof signals, and proximity of the neighborhood node drive path to thehardline coaxial cable plant of the neighborhood node under evaluation;in one example, the test signal may be broadcast with relatively steadypower on the order of approximately 2 Watts to 4 Watts (duringevaluation of ingress mitigated node BT-11 shown in FIG. 24, a powerlevel of the transmitter 135 for transmitting the test signal from themobile broadcast apparatus 130 was approximately 2 Watts). A suitablenon-limiting example of CB radio serving as the transmitter 135 isprovided by the Cobra Roadtrip (seehttps://www.cobra.com/detail/hh-road-trip-handheld-cb-radio-with-weather-and-soundtracker.cfm).

In various embodiments, the transmitter 135, alone or in combinationwith the processing unit(s) 134, may be configured to transmit the testsignal in a variety of manners. For example, in one implementation, themobile broadcast apparatus 130 transmits the test signal as anessentially continuous carrier wave having a carrier frequency in theupstream path bandwidth, with no information modulated onto the carrierwave (i.e., simply a “bare tone”). In other embodiments discussedfurther below, one or both of the transmitter 135 and the processingunit(s) 134 may be configured such that the mobile broadcast apparatus130 broadcasts the test signal at one or more different power levels(e.g., in some cases having sufficiently low power so as to not requirelicensure from one or more regulatory authorities), one or moredifferent fixed or varying carrier frequencies (e.g., discrete orsimultaneous multiple carriers as a function of time), and/or using anyone or more of a variety of modulation techniques (e.g., amplitudemodulation, frequency modulation, phase modulation, QAM, pulsed testsignals, time division multiplexed test signals, spread-spectrummodulated test signals, etc.).

Since the mobile broadcast apparatus 130 broadcasts a test signal in agiven neighborhood node of a cable communication system at a known timeand/or for a known time period (e.g., either continuously over a giventime period, or periodically at known times), the identification ofpotential points of ingress in the neighborhood node does not depend onpotentially intermittent, random and unpredictable signals generated byan actual ingress source. Thus, the mobile broadcast apparatussignificantly reduces the time and effort needed to identify potentialpoints of ingress in a cable communication system.

B. Portable or Handheld Field Device

In phase 2 of an ingress detection and remediation method according toone embodiment of the present invention (discussed further below inconnection with FIG. 48), a field technician 148 uses informationcollected and/or generated during phase 1 activity (e.g., a neighborhoodnode ingress map, discussed further below in connection with FIGS. 33through 47) to locally home-in on and verify specific locations ofingress in a neighborhood node under evaluation to particularly identifyand isolate one or more faults in the neighborhood node (e.g., faultysystem elements) that are directly responsible for ingress. Inparticular, based on one or more maps generated in phase 1, afield-technician 148 may proceed to one or more particular locations inthe neighborhood node where the map(s) indicate potential points ofingress, and employ a portable or handheld field device 140 as a testinstrument to home-in on potential ingress points by traversing a targetingress problem area with greater geographical resolution (e.g., onfoot, and/or with the aid of a “bucket” truck in the case of hardlinecoaxial cable plant components disposed aerially on utility poles).

As with other components of the ingress detection system 100, in someimplementations the portable or handheld field device 140 may include orbe associated with a computing device, such as a portable computer,tablet device, a personal digital assistant (PDA), smart phone, cellularradio telephone, mobile computing device, touch-screen device, touchpaddevice, or generally any device including, or connected to, a processorand display. More specifically, the field device 140 may include one ormore antenna 141 and a transmitter 143 coupled to the antenna totransmit a local test signal in an upstream path bandwidth of theneighborhood node under evaluation. The field device also may includeone or more communication interfaces 142 to receive various informationincluding, but not limited to: 1) one or more neighborhood node ingressmaps; 2) one or more other maps/other information associated with theneighborhood node ingress map(s) to facilitate fault location; and/or 3)signal information relating to signal amplitudes representing strengthsof a received upstream local test signal at the headend of the cablecommunication system, based on the local test signal transmitted by thetransmitter 143 and ingress of the local test signal into one or morefaults in the hardline coaxial cable plant, one or more subscriberservice drops, and/or one or more subscriber premises.

The field device 140 also may include one or more display devices 145 todisplay one or more neighborhood node ingress maps and/or othermaps/images corresponding to the geographic area covered by theneighborhood node ingress map, so as to facilitate an orientation of theingress profile in the neighborhood node under evaluation to theenvironmental surroundings and/or cable communication systeminfrastructure. The display device 145 also may display one or moreindications, based at least in part on the received signal information,corresponding to the signal amplitudes representing strengths of thereceived upstream local test signal at the headend of the cablecommunication system. In some implementations, the field device 140 alsomay include memory 146 and one or more processing units (CPUs) 144 tofacilitate one or more of the reception, processing, display and/orindication of various information, as well as transmission of the localtest signal.

In one exemplary implementation, the field device 140 has a portable orhandheld housing for at least the transmitter, the communicationinterface(s), and display device(s), and may further include a userinterface 147 (e.g., a keypad, touch screen, etc.) to allow the fieldtechnician to operate the device and/or enter in information relevant tothe ingress detection and remediation process. In various aspects, theantenna 141 may be an integral part of the field device; alternatively,the antenna 141 may not necessarily be mechanically coupled to the fielddevice, but may be instead carried by the technician as a separate unitand electrically coupled to the transmitter of the field device 140.Whether the antenna 141 forms an integral part of the field device 140or not, in one aspect the antenna 141 may be a directional antenna toprovide appropriate strength and directionality of the transmitted localtest signal and thereby facilitate identifying particular points ofingress. In another exemplary implementation, the field device 140 maybe implemented by a combination of a small transmitter/antenna (e.g., a“walkie-talkie”) carried and operated by a first technician on a buckettruck in the air proximate to elements of a hardline coaxial cable plantmounted on utility poles, and a separate portable computing deviceoperated/monitored on the ground by a second technician (and incommunication with the first technician, e.g., to provide feedbackregarding the signal strength received at the headend).

As noted earlier, in one aspect the transmitter 143 of the field device140, in a manner similar to that of the mobile broadcast apparatus 130,alone or in combination with the processing unit(s) 144, may beconfigured to transmit the local test signal in a variety of manners(e.g., a continuous unmodulated carrier wave; modulated signal such asamplitude/frequency/phase/QAM modulated, spread spectrum, TDM, pulsesignal; at various power levels; at one or more carrier frequencies; attime-dependent/varying carrier frequencies, etc.). In oneimplementation, the field device 140 may be configured to transmit thelocal test signal without significantly interfering with operativesignaling in the upstream path bandwidth from one or more subscriberpremises in the neighborhood node under evaluation (e.g., via an“unused” frequency in the upstream path bandwidth, and/or via modulationsuch as spread spectrum, TDM, pulse signal, etc.).

The field technician 148 employs the field device 140 to transmit thelocal test signal as the technician traverses (e.g., walks around, ordrives in close proximity to) the target ingress problem area, or“sweeps” the field device across/along a particular system component insufficiently close proximity to the component. The field device 140 thenreceives, in essentially real time (e.g., via the communication network150), signal amplitudes representing a strength of a received upstreamlocal test signal at the headend of the cable communication system, toprovide feedback on the degree of ingress present within the targetproblem area. As discussed above, any of a variety of communicationmethodologies may be employed by the communication network 150 toprovide this feedback to the field device 140 (e.g., two-way radio,telecommunications, Internet access, etc.). The feedback can in turn beconveyed by the field device 140 to the field technician in any of avariety of manners (e.g., audibly, visually or both); for example, theCPU(s) 144 may control the display device(s) 145 of the field device 140to display one or more indications representing the feedback asalphanumeric and/or graphic information (e.g., numbers, graphs,simulated meters, reproduced display(s) of the analyzer 110 and/or thetest and/or monitoring equipment 256, etc.). Alternatively, or inaddition, the display device(s) may include one or more light emittingdiodes (LEDs) of different colors to simulate a scale representingreceived signal strength, and/or the user interface of the field devicemay include a speaker to provide one or more audible indications (e.g.,of a received signal strength exceeding a predetermined thresholdvalue). Accordingly, it should be appreciated that one or moreindications corresponding to the signal amplitudes representingstrengths of the received upstream local test signal at the headend ofthe cable communication system may be conveyed to the technician via thefield device 140 in any of a variety of manners.

C. Analyzer/Test Equipment

As shown in FIG. 28, the analyzer 110 (e.g., a spectrum analyzer, aparticularly tuned signal receiver, etc.) may be located at headend 162of a cable communication system (or alternatively coupled to a junctionbetween the hardline coaxial cable plant and an optical/RF bridgeconverter of a given neighborhood node) so as to monitor the upstreampath and record signal amplitudes as a function of time at the one ormore test signal frequencies of the test signal broadcast by the mobilebroadcast apparatus 130. The analyzer 110 may include one or moreprocessing units (CPU) 114, memory 116, one or more communicationinterfaces 112, and a display device 111. The analyzer 110 may beimplemented in various form factors, examples of which include, but arenot limited to, a special purpose device (e.g., a particularly tunedsignal receiver with appropriate filtering components; a spectrumanalyzer) and/or a computing or telecommunications devices such as aportable computer, tablet device, a personal digital assistant (PDA),smart phone, cellular radio telephone, mobile computing device,touch-screen device, touchpad device, or generally any device including,or connected to, a processor and display. One example of a suitablespectrum analyzer is given by a Hewlett Packard spectrum analyzer (e.g.,model HP 8591C) communicatively coupled to a computing device includinga communication interface; more specifically, the HP spectrum analyzermay be connected via a serial communication bus to a laptop computerexecuting an HP API to request and log signal amplitudes (e.g., in unitsof dBmV) with a corresponding time stamp. Another suitable example of aspectrum analyzer is given by an Agilent n9000A spectrum analyzer. Insome implementations, as discussed above test and/or monitoringequipment 256 may be used in addition to, or alternatively to, theanalyzer 110; one example of suitable test and/or monitoring equipmentis given by the JDSU PathTrack™ HCU-200 Integrated Return PathMonitoring Module (e.g., seehttp://www.jdsu.com/ProductLiterature/hcu200_ds_cab_tm_ae.pdf).

In one embodiment, one or more base technicians 118 may be responsiblefor analyzing the signals received by the analyzer 110 and/or the testand/or monitoring equipment 256. For example, a, base technician 118 maybe responsible for determining whether the signals received at headend162 indicate that ingress may be occurring at one or more locations inthe cable communication system (e.g., proximate to where the mobilebroadcast apparatus 130 or handheld transmitter 140 are located andtransmitting respective test signals). Consequently, base technician 118may use analyzer 110 to examine the signals transmitted by mobilebroadcast apparatus 130 or handheld transmitter 140 and received at theheadend 162, and may also use the test and/or monitoring equipment 256to monitor the integrity of physical communication channels conveyingupstream information from subscriber premises in the neighborhood nodeunder evaluation.

D. Processor

Processor 120 may be any electronic device that can analyze and/orprocess data and generate various information (e.g., one or more maps orimages) relating to the ingress mitigation methodology discussed hereinaccording to various embodiments of the invention. Processor 120 mayinclude or be associated with a computing device, such as a portablecomputer, personal computer, general purpose computer, server, tabletdevice, a personal digital assistant (PDA), smart phone, cellular radiotelephone, mobile computing device, touch-screen device, touchpaddevice, and the like. In some implementations, the processor 120 may beco-located with, and communicatively coupled to, the analyzer 110 and/orthe test and/or monitoring equipment 256 at the headend of the cablecommunication system. It other implementations, one or more processors120 need not necessarily form part of the ingress detection system 100,but merely may be in communication with other elements of the systems(e.g., via the communication network 150).

In one embodiment, the processor 120 includes one or more processingunits (CPU) 124, memory 126, one or more communication interfaces 122,and display device 121. Via execution by the processor's processingunit(s) 124 of processor-executable instructions (e.g., stored in thememory 126), the processor may perform a computer-implemented method forfacilitating detection of potential points of ingress in a givenneighborhood node under evaluation. In particular, in connection withphase 1 activity, the processor 102 may receive (e.g., via thecommunication interface(s) 122, from one or more of the mobile broadcastapparatus 130, the analyzer 110, and the test and/or monitoringequipment 256) or otherwise access (e.g., from memory 126) a firstelectronic record (e.g., generated in the field by the mobile broadcastapparatus 130) including geographic information for a plurality oflocations in the field at which a test signal is broadcast in anupstream path bandwidth of the neighborhood node (e.g., respectivepositions of the vehicle 133 along a neighborhood node drive path 305 asit broadcasts a test signal). The processor further may receive orotherwise access a second electronic record including a plurality ofsignal amplitudes recorded at a headend of the cable communicationsystem, representing a strength of a received upstream test signal atthe headend based on the broadcasted test signal.

In one implementation, via execution by the processor's processingunit(s) of processor-executable instructions, the processer then maymerge the first electronic record and the second electronic record so asto generate a third electronic record including at least the geographicinformation for the plurality of locations at which the test signal isbroadcast, and the plurality of signal amplitudes representing thestrength of the received upstream test signal. The processor may thenprocess the third electronic record so as to generate a neighborhoodnode ingress map including a first graphical representation of theneighborhood node drive path 305 traversed by the mobile broadcastapparatus 130, and a second graphical representation (e.g., superimposedor overlaid on the first graphical representation) of the plurality ofsignal amplitudes so as to illustrate test signal ingress of the testsignal into various elements of the neighborhood node (particularly thehardline coaxial cable plant). More generally, as discussed in greaterdetail below, the processor may perform analysis and processing ofgeographic information relating to vehicle position along a neighborhoodnode drive path, signal amplitudes representing received upstream testsignal strength, and/or other information to in turn provide a wealth ofinformation relating to potential points of ingress in a neighborhoodnode under evaluation, including different visual renderings relating topotential points of ingress.

Map information for rendering graphical representations of signalingress in one or more neighborhood nodes of a cable communicationsystem may be communicated by the processor 120 to any one or more ofthe analyzer 110, mobile broadcast apparatus 130, or portable/handheldfield device 140 shown in FIG. 28, and/or maps may be displayed locallyon the processor's display device 121. In some exemplaryimplementations, map data may be saved and communicated as .png files,but it should be appreciated that a variety of graphical formats may beemployed (including formats that allow for transparency for overlayingmultiple “layers” of map information and/or image information, such assatellite or aerial images).

III. PHASE 1—INGRESS DETECTION AND MAPPING

FIG. 29 provides a flow chart to graphically illustrate a method forfacilitating ingress detection and mapping (e.g., “phase 1” activity),according to embodiments of the present invention. Various aspects ofthis method may be implemented by components of the ingress detectionsystem 100 introduced above in FIG. 28, in connection with a cablecommunication system similar to that shown in FIG. 1 or 27.

In the method outlined in FIG. 29, at block 210 a test signal isbroadcast by the mobile broadcast apparatus 130 in the upstream pathbandwidth (e.g., 5 MHz to at least 42 MHz) of a given neighborhood nodeunder evaluation. With reference again to the cable facilities map 310shown in FIG. 24 (of the ingress mitigated node BT-11) as well as FIG.28, the mobile broadcast apparatus 130 (e.g., the vehicle 133 equippedwith the transmitter 135) proceeds along a neighborhood node drive path305 proximate to the hardline coaxial cable plant 180 so as toeffectively traverse and ensure substantially full coverage of theneighborhood node. As noted above and observed in FIG. 24 (and FIG. 25),cable communication system infrastructure within the neighborhood node,and particularly elements of the hardline coaxial cable plant deployedin the neighborhood node, essentially follow existing roadways in thegeographic area covered by the neighborhood node (e.g., deployedsubstantially or at least partially above ground on utility polesflanking and proximate to roadways).

In example implementations, as the hardline coaxial cable plant (as wellas the subscriber premises and associated subscriber service drops) mayinclude one or more faults that may contribute in some manner toallowing for ingress (i.e., faults may be located anywhere along thehardline coaxial cable plant, even in areas of the neighborhood nodewith a relatively low number of households passed and/or relatively lowsubscriber penetration), the neighborhood node drive path 305 iscarefully chosen to afford substantially full/complete coverage of theneighborhood node. In one exemplary implementation, each of the roadwayswithin the neighborhood node (e.g., see the roadways of the ingressmitigated node BT-11 as indicated on the cable facilities map 310 shownin FIG. 24) constitutes a portion of the neighborhood node drive path305 over which the mobile broadcast apparatus 130 traverses. As themobile broadcast apparatus 130 proceeds along the neighborhood nodedrive path 305, a test signal is broadcast from the transmitter 135 at aplurality of locations distributed along at least a substantial portion(and preferably the entirety) of the neighborhood node drive path,wherein the test signal has one or more test signal frequencies fallingwithin the upstream path bandwidth. Additional details regarding thetest signal and various options for generating/broadcasting same arediscussed in greater detail below in Section III.A.

In block 212, as the mobile broadcast apparatus 130 proceeds along theneighborhood node drive path 305, respective positions at which the testsignal is broadcast are recorded (e.g., as a function of time) togenerate a first record of geographic information associated withtransmission of the test signal in the neighborhood node. For example,with reference again to FIG. 28, a navigation device 132 (e.g., a globalpositioning system or GPS) associated with the mobile broadcastapparatus 130 may identify the geographical position of the mobilebroadcast apparatus 130 as a function of time, as the test signal isbroadcast, and record latitude and longitude coordinates for same. Inone example, respective positions of the mobile broadcast apparatus arerecorded together with a corresponding time stamp.

It should be appreciated that, according to one aspect of thisembodiment, the local recording of geographic information (e.g., GPSlatitude and longitude coordinates) by the mobile broadcast apparatus atrespective positions along a substantial portion, and preferably theentirety, of the neighborhood node drive path significantly facilitatesthe generation of accurate and complete neighborhood node ingress mapsillustrating potential points of ingress in the neighborhood node, asdiscussed in greater detail below. In contrast, transmitting suchgeographic information to the headend using the broadcast test signalitself as a carrier for the geographic information (i.e., the geographicinformation is encoded on the test signal itself via modulation of thetest signal) may result in the geographic information not being receivedat the headend (and hence not being completely or accurately recorded).In particular, in situations involving relatively low (but nonethelesssignificant) degrees of ingress at a particular location in theneighborhood node, a test signal that is broadcast at this location andcarrying any particular information, such as GPS coordinatescorresponding to respective positions of the mobile broadcast apparatus,likely will not be received with sufficient strength and detected at theheadend. Accordingly, many positions of the mobile broadcast apparatusas it traverses the neighborhood node drive path would be “lost,” i.e.,not part of the collected information, as any information encoded on thetest signal carrier would not be completely or accurately received, ifat all.

In view of the foregoing, in some exemplary embodiments of phase 1activity, the broadcast test signal does not include (e.g., havemodulated thereon) the geographic information for respective positionsat which the test signal is broadcast by the mobile broadcast apparatus130. In this manner, the generation in the field of a first record ofgeographical information corresponding to respective positions of themobile broadcast apparatus along at least a substantial portion of thefirst neighborhood node drive path does not rely on the integrity of thebroadcast test signal itself, nor does it rely on reliable reception ofthe test signal at the headend of the cable communication system. Inthis fashion, a more reliable, complete and accurate record is providedof geographic information associated with respective positions in theneighborhood node at which the test signal is broadcast.

At block 214, also as the mobile broadcast apparatus 130 proceeds alongthe neighborhood node drive path 305 of the neighborhood node underevaluation, a plurality of signal amplitudes are recorded by theanalyzer 110 (coupled to a first junction of the CMTS and the headendoptical/RF converter, or a second junction of the hardline cable plantand the optical/RF bridge converter of the neighborhood node; see FIGS.1 and 2), wherein the signal amplitudes represent a strength of areceived upstream test signal as a function of time. The receivedupstream test signal itself arises from the test signal broadcast by themobile broadcast apparatus 130, and test signal ingress of the testsignal into one or more faults in the neighborhood node (andparticularly one or more faults in the hardline coaxial cable plant).More specifically, with reference to FIG. 28, a signal receiverpositioned at the headend 162, such as analyzer 110, monitors theupstream path bandwidth of the neighborhood node under evaluation, andparticularly monitors a range of frequencies within which (or one ormore specific frequencies at which) the test signal is broadcast. In oneaspect, analyzer 110 records the plurality of signal amplitudes,together with a second plurality of corresponding time stamps at whichthe signal amplitudes are recorded, so as to generate a second record,wherein respective signal amplitudes represent a strength of thereceived upstream test signal as a function of time. Generally speaking,larger received amplitudes implicate a greater degree of possibleingress.

As noted above, in some implementations each of the first record ofgeographic information corresponding to vehicle positions along thedrive path and the second record of signal amplitudes of the receivedupstream test signal includes corresponding time stamps for the recordedinformation. However, it should be appreciated that embodiments of thepresent invention are not limited in this respect, and such records maybe generated in a variety of manners to facilitate subsequent processingand coordination of the information. For example, in one implementation,the geographic information corresponding to respective positions of thevehicle along the drive path may be recorded in the first record (e.g.,by the mobile broadcast apparatus 130) as a first ordered sequence ofpoints, and the plurality of signal amplitudes of the received upstreamtest signal may be recorded in the second record (e.g., by the analyzer110) as a second ordered sequence of points. In one aspect, the firstordered sequence of points is indexed to the second ordered sequence ofpoints; in another aspect, the first ordered sequence of points and thesecond ordered sequence of points respectively may be sampled at a sametime. In various aspects, the processor 120 of the system 100 shown inFIG. 28 may be configured to control (e.g., via the communicationnetwork 150) the navigation device 132 of the mobile broadcast apparatus130 and the analyzer 110 to synchronize acquisition of the first andsecond records, receive the first and second records, and/or otherwiseprocess the information therein so as to coordinate the geographicinformation and the plurality of signal amplitudes.

In another exemplary implementation of this embodiment, the vehicle 133is driven (or otherwise operated) such that the mobile broadcastapparatus 130 traverses at least a substantial portion of theneighborhood drive path during a concerted time period or single“drive-through” of the neighborhood node so as to generate the firstrecord and the second record. In other implementations, multiple“partial drive-throughs” may be conducted such that the mobile broadcastapparatus 130 proceeds along different portions of the drive path duringdifferent time periods/at different times (e.g., based on one or more ofdriver/technician work shifts, weather conditions, constructionsconditions, other conditions that may affect navigability of the drivepath, temporal cycles in terrestrial signals that may give rise toingress, etc.) so as to generate corresponding portions of the first andsecond records. Such partial drive-throughs may in some instances coveroverlapping portions of the neighborhood node drive path. In any case,the respective portions of the first and second records thusly generatedare then combined (and in some cases analyzed/processed, e.g., to omitredundancy or average multiple readings) to generate “full” first andsecond records representing coverage for at least a substantial portion,if not the entirety, of the neighborhood node drive path.

At block 215, one or both of the first and second records optionally maybe electronically analyzed and/or processed (e.g., by the processor 120of the system 100), alone or in combination with other information(e.g., stored in memory 126 of the processor 120 or otherwise accessedby the processor 120 via the communication network 150), so as tofacilitate identification of one or more possible faults in the systemconstituting potential points of ingress. Various optional processingand analysis techniques that may be employed by the processor 120 inblock 215 are discussed in greater detail below in Section III.B.

At block 216, based on the first record of the respective positions ofthe mobile broadcast apparatus 130 as a function of time, and the secondrecord of the plurality of signal amplitudes representing a strength ofthe received upstream test signal as a function of time, the processor120 of the system 100 electronically generates a neighborhood nodeingress map for the neighborhood node under evaluation. Examples ofneighborhood node ingress maps according to various embodiments of thepresent invention are discussed in greater detail below in connectionwith FIGS. 33 through 47. In one aspect, the neighborhood node ingressmap may include a first graphical representation of the neighborhoodnode drive path 305; in another aspect, the neighborhood node ingressmap may include a second graphical representation, overlaid on the firstgraphical representation, of the plurality of signal amplitudes alongthe neighborhood node drive path so as to illustrate the test signalingress of the test signal in the neighborhood node (and particularlyinto the hardline coaxial cable plant). To this end, the processor 120may merge the information in the first and second records to formordered sets. More specifically, in one example the first record and thesecond record are merged (e.g., based on an index or respective timestamps) so as to generate a third record including both the geographicinformation and plurality of signal amplitudes. Accordingly, the thirdrecord may include an ordered set of multiple entries each having threeor four dimensions or parameters (e.g., [LAT, LONG, AMPLITUDE] or [LAT,LONG, AMPLITUDE, TIME]), from which the processor 120 may generate theneighborhood node ingress map to show the route(s) traversed by themobile broadcast apparatus 130 on the neighborhood node drive path 305,and relative degrees of ingress at different positions along theneighborhood node drive path.

With respect to a third record including an ordered set of data tofacilitate generation of a neighborhood node ingress map, a timecoordinate may or may not be included in such an ordered set. Forexample, in one implementation, a time coordinate may be employed tovisually render a dynamic “recreation” of the phase 1 process (e.g.,create a “replay” of the drive-around route through the neighborhoodnode taken by the mobile broadcast apparatus). In other implementations,the geographic information may be received and logged at a particularperiodicity (e.g., one second intervals), and time coordinatescorresponding to respective time stamps may not be necessary to rendersuch a “replay” if consecutive geographic coordinates are presumed torepresent predetermined logging intervals (e.g., approximately onesecond intervals). Additionally, as noted above, the first and secondrecords may not include corresponding time stamps for informationtherein, but instead may be indexed to each other in some manner (e.g.,based on a common or synchronized sampling rate, or particular number ofdata points acquired in the respective records). In any event, it shouldbe appreciated that such a third record, if created by the processor 120pursuant to merging the first and second records, may or may not includea time parameter according to various embodiments. Additional detailsregarding various processing options implemented by the processor 120 inconnection with the information provided by the first record and secondrecord are provided below in Sections III.B and III.C.

In different embodiments, various activity relating to phase 1 asdiscussed above may be performed “actively” or intentionally, oralternatively in a more passive manner. For example, a technician maydirect the mobile broadcast apparatus 130 through a specified area(e.g., along a neighborhood node drive path traversing a neighborhoodnode) for the express purpose of generating the first record and thesecond record discussed above, and possibly gathering other information(discussed in greater detail below) in connection with ingress detectionand/or remediation. In some implementations, such activity may beperformed by relatively lower-skilled technicians to cover largegeographic areas relatively quickly and inexpensively, perhaps as partof an ongoing preventative maintenance program. This approach also maybe employed, if even for a small segment of hardline coaxial cableplant, so as to gather information about a particular area of interestduring demand maintenance activity.

In other implementations, various activity relating to phase 1 may bemore passively executed. For example, technicians performing regular orroutine maintenance or fulfillment activities may be outfitted such thatthey “passively” gather data relating to geographic position in aparticular neighborhood node and corresponding received signal strengthdue to a broadcast test signal as they move (e.g., in a vehicle orotherwise) through different geographic areas that may overlap with oneor more neighborhood nodes of potential interest with respect to ingressmitigation. This passive approach to information gathering may, overtime, facilitate the collection of ingress-relevant information over asignificant portion of a cable communication system (e.g., spanning oneor more neighborhood nodes) without allocating dedicated personnel tosuch a task. Such an approach may be entirely passive, or may includepartial routing direction from a supervisor/system operator (e.g., asmay be provided by the processor 120) so as to increase coverage, whilestill having a relatively low impact on technician resources. Additionalconcepts relating to active and passive information gathering techniquesare discussed further below in connection with “Process Guides.”

A. Test Signal(s)

With reference again to block 210 of FIG. 29, a variety of test signalbroadcasting techniques may be employed in accordance with variousembodiments of the present invention (and these techniques similarly maybe applied to transmission of a local test signal during phase 2activity, discussed in detail below).

In one aspect, the test signal is broadcast so as not to interrupt orotherwise interfere with operative signals (e.g., upstream informationbeing conveyed by one or more upstream physical communication channels)from one or more subscriber premises in the neighborhood node to theheadend 162. To this end, in one example the test signal may bebroadcast as a carrier wave (e.g., a simple tone) on an unused frequencyin the upstream path bandwidth (e.g., a frequency that is not currentlyin use by, or assigned to, any subscriber modems on the neighborhoodnode under evaluation). As discussed above, in one embodiment the testsignal is not modulated or otherwise encoded with any geographicinformation representing positions of the mobile broadcast apparatusalong the neighborhood drive path, so as to avoid gaps or losses in suchgeographic information due to significantly attenuated or non-existentsignal amplitudes corresponding to the test signal as monitored by theanalyzer 110.

In other examples, the test signal alternatively may be modified ormodulated to significantly reduce potential interference with othersignals on the network, particularly in the upstream path bandwidth.Examples of modulation techniques that may be employed to generate thetest signal include, but are not limited to, amplitude modulation,frequency modulation, phase modulation, digital modulation techniquessuch as phase-shift-keyed (PSK) modulation or quadrature amplitudemodulation (QAM), spread spectrum modulation and time divisionmultiplexing (TDM).

In connection with time division multiplexing, in one exemplaryimplementation the CMTS 170 of the cable communication system maycontrol subscriber modems in the neighborhood node according to a TDMAor ATDMA access protocol, such that a physical communication channelassigned to the modems includes a plurality of time slots (referred toin DOCSIS as “minislots”). In one aspect, the plurality of time slotsare segregated so as to include a plurality of subscriber premises timeslots and at least one dedicated time slot for the test signal. Thesubscriber modems are assigned (e.g., by the CMTS at the headend of thecable communication system) respective subscriber premises time slots totransmit upstream information in the upstream path bandwidth. Theprocessor 120 of the ingress detection system 100 may be incommunication with the CMTS (e.g., via the communication network 150) soas to control the mobile broadcast apparatus 130 to broadcast the testsignal during the dedicated time slot. In this manner, interference ofthe test signal with the upstream information in the upstream pathbandwidth may be avoided.

In some embodiments, the test signal may be broadcast by the mobilebroadcast apparatus at a sufficiently low power as transmitted by thetransmitter so as not to require licensure by one or more regulatoryauthorities (e.g., in the U.S., the Federal Communication Commission,see “Understanding the FCC Regulations for Low-Power, Non-LicensedTransmitters,” OET Bulletin 63, October 1993, FCC Office of Engineeringand Technology, Washington, D.C., which is hereby incorporated byreference herein in its entirety). Also, since particular regions ofinterest in the upstream path bandwidth with respect to ingress includefrequencies below approximately 20 MHz, and more particularly below 18MHz, and more particularly below 16.4 MHz, and more particularly below10 MHz, in some embodiments the test signal may be broadcast at one ormore test signal frequencies between approximately 5 MHz at the low endof a spectral region of interest, and approximately 10 MHz to 20 MHz atthe high end of the spectral region of interest.

As discussed above, faults in one or more of the hardline coaxial cableplant, subscriber service drops and subscriber premises of a givenneighborhood node may viewed as resonance structures (e.g., RC or RLCcircuits) having particular frequency-dependent and/orfrequency-specific characteristics. Accordingly, in some embodiments,employing one or more test signals having different test signalfrequencies and/or a time-varying test signal frequency may in someinstances facilitate identification of faults having suchfrequency-dependent and/or frequency-specific characteristics (byexploiting the frequency response of the resonance structuresconstituting the faults). For example, in one implementation, as thetest signal is broadcast by the mobile broadcast apparatus, the testsignal frequency may be varied as a function of time, across at least aportion of the upstream path bandwidth. More specifically, the testsignal may have a test signal frequency having one value that varies(e.g., continuously or discretely) as a function time; alternatively,multiple test signals having respectively different test signalfrequencies may be broadcast simultaneously. In yet anotherimplementation, the test signal may be broadcast as a spread spectrumsignal (e.g., frequency-hopping spread spectrum or FHSS, direct-sequencespread spectrum or DSSS, time-hopping spread spectrum or THSS, and chirpspread spectrum or CSS), which employs a pseudonoise code to spread anarrowband signal over a relatively wider band of frequencies. Ingressarising from entry of a spread spectrum test signal via one or morefrequency-dependent or frequency-specific faults may in someimplementations be derived from data provided by demodulation tuners atthe head end that report on “equalizer stress” or similar data inconnection with equalizers employed for adaptive equalization asdiscussed above.

In yet other embodiments, rather than avoiding portions of the upstreampath bandwidth in which operative signals are being transmitted (e.g.,via one or more physical communication channels having particularcarrier frequencies) representing upstream information from one or moresubscriber premises, one or more test signals may be broadcast by themobile broadcast apparatus at one or more test signal frequencies thatfall within a frequency range occupied by channels in which suchoperative signaling is occurring. In this manner, ingress that may bespecifically affecting a range of frequencies in which one or moreupstream physical communication channels are deployed may beparticularly identified so as to facilitate remediation of correspondingfaults allowing for such ingress. In one aspect of such embodiments, thetest signal frequency may be varied as a function of time across asubstantial portion of the frequency range of the operative signaling inthe upstream path bandwidth.

In yet other embodiments, frequency division multiplexing techniques maybe employed in connection with broadcasting by the mobile broadcastapparatus of one or more test signals at different frequencies. In oneaspect of such embodiments, distinct (e.g. unique) test signalfrequencies may be assigned to respective field technicians directingthe mobile broadcast apparatus along a particular neighborhood nodedrive path, or alternatively may be assigned to vehicles in which themobile broadcast apparatus is situated to provide a mode ofdifferentiating the source of the test signal. This frequencymultiplexing technique allows simultaneous test signals to be sent bydifferent technicians, even in adjacent neighborhood nodes, while stillallowing for the system to provide a “fingerprint” to distinguish therespective signals from different technicians and while preventinginterference between the test signals. The different test signalfrequencies may include discrete signals transmitted concurrently orsequentially and may be at any arbitrary spectral resolution deemedpractical. Additional signifying elements such as modulationdistinctions, time division multiplexing and phase division multiplexingmay also be applied to provide technician or test vehicle specificsignal “fingerprints”.

In some embodiments, interferometric techniques may also be employed inconnection with transmission of multiple test-signals. Morespecifically, when multiple different-frequency test signals aretransmitted, the interference patterns resulting from the mixing of suchsignals as they respectively enter one or more hardline cableplant-related or subscriber-related faults may be identified andanalyzed to reduce ambiguity in the signals (particularly those that arein close geographic proximity to one another and of similarreceptivity), thereby allowing more accurate positioning of the pointsof ingress relative to the transmitter.

In yet other embodiments, directional antennae may be employed inconnection with the mobile broadcast apparatus 130 (as well as theportable/handheld field device 140). By using a directional antennatogether with positioning data including, but not limited to, geographicposition, bearing, pitch, roll and yaw, reduces amplitude vs. proximityambiguity by narrowing the field within which elements of the cablecommunication system are exposed to the test signal, thereby reducingopportunities for multi-point reception. Additionally, some ingresspoints exhibit directionally-specific receptivity, which may be directlydetected and more accurately modeled with the use of directionalantennae, leading to more accurate positioning and classification ofingress points. A single antenna that mechanically sweeps though theplane of transmission during a specified period may be used to implementa multi-point test frequency reception method. An antenna array capableof altering its directionality through electronic variations (e.g.,variable loading of its transmission elements, or similar approach) mayalso be used to achieve this function. Alternatively, an array of fixedantennae with some angular relationship to one another within the planeof transmission (e.g., four antennae mounted at 90° angles to oneanother) may be used to receive directionally specific signaltransmissions. A rotating directional antenna may be employed inconnection with implementing triangulation techniques. Headings tospecific points of ingress may be inferred from the peak amplitudeduring a sweep through the transmission plane. Headings to a source frommultiple transmission locations may be used in conjunction totriangulate the fault position.

In yet other embodiments, the test signal may be broadcast as at leastone pulsed test signal so as to mitigate significant interference withoperative signaling (e.g., upstream information from subscriberpremises) in the upstream path bandwidth. Pulsed or discrete time statetest signals may be employed, in lieu of continuously transmitted ones,in various aspects for a variety of reasons (e.g., reduced systeminterference, inherent feature of a modulation scheme, etc.), and mayspecifically be used to assist in positioning points of ingress in thecable communication system relative to the test-signal transmitter. Tothis end, a duration of one or more pulses of the pulsed test signal maybe less than a symbol length of the operative signaling (e.g., based onthe modulation order of the QAM RF signal carrying upstreaminformation). A sufficiently brief test-signal pulse would be receivedby the amplitude monitoring equipment in the headend (e.g., the analyzer110) as a series of pulses (of varying amplitudes), each correspondingto a particular, and varying-length path taken from each fault throughwhich the test signal enters the cable communication system. The timedifferences of arrival (TDOA), or relative arrival times of thesepulses, may be used to infer information about their positions relativeto the test signal transmitter and each other, allowing increasedaccuracy in fault positioning. The TDOA may also be measured using testsignal modulation schemes that have discrete time states (such as QAMsymbols; see ‘Hyperbolic Location’ under ‘Positioning’ discussed furtherbelow).

B. Signal Processing

With reference to block 215 of the method shown in FIG. 29, variousprocessing options may be implemented by the processor 120 of theingress detection system 100 shown in FIG. 28, in connection with thefirst record of geographic information representing respective positionsof the mobile broadcast apparatus 130 (as it broadcasts the test signal)and the second record of the plurality of signal amplitudes representinga strength of the received upstream test signal as a function of time(e.g., as measured by analyzer 110).

It should be appreciated, however, that merely relying on theinformation contained in one or both of the first and second recordsthemselves, with relatively nominal or no significant processing oranalysis, provides valuable insight into possible faults constitutingpotential points of ingress in a cable communication system. Thus,approaches involving relatively nominal or no significant processingnonetheless may be employed in some embodiments to identify potentialpoints of ingress more quickly, effectively and easily than byconventional techniques.

In some examples, in addition to one or both of the first and secondrecords, other information may be used by the processor 120 tofacilitate processing and/or analysis in connection with one or both ofthe first and second records (which information in some instances may becommunicated to the processor 120 via the communication network 150shown in FIG. 28 and/or stored in memory 126 of the processor 120).Examples of such other information include, but are not limited to: 1)one or more cable facilities maps (e.g., see FIGS. 24 and 25); 2) one ormore street maps showing various roads and rights-of-way within thegeographic area covered by the neighborhood node; 3) one or more parcelmaps showing various roads and rights-of-way within the geographic areacovered by a neighborhood node as well as households passed in theneighborhood node; 4) one or more aerial images showing varioustopographical features in the neighborhood node (e.g., including roadsand rights-of-way within the geographic area covered by a neighborhoodnode as well as households passed in the neighborhood node); 5) ambientingress information corresponding to a strength of ambient ingress in atleast a portion of the geographic area covered by the neighborhood node;6) environmental information (e.g., weather information, terraininformation) relating to the geographic area covered by the neighborhoodnode; 7) various subscriber information relating to one or moresubscriber premises in the neighborhood node, which in some cases may beprovided by the cable communication system operator (e.g., MSO);examples of such subscriber information may include, but are not limitedto: subscriber identification (e.g., a subscriber list); subscriberservice plans for respective subscribers (e.g., types of services ordata usage plans); historical changes in subscriber service ormaintenance records; “special status” indications to indicatefrequent/periodic problem issues in connection with service (“troubletickets”), and/or a particular type of subscriber or subscriberpremises, such as a hospital, a school, a military or governmentbuilding, or other “VIP” status); and 8) various information provided byDOCSIS equipment such as subscriber modems and demodulation tuners atthe headend.

In general, various processing and analytical techniques applied to oneor both of the first and second records, and in some instancesadditional information as discussed above, facilitates identification ofpossible faults constituting potential points of ingress in the cablecommunication system, and particularly in the hardline coaxial cableplant of a given neighborhood node under evaluation. As discussed indetail below, the results of such analysis and processing may takeseveral forms, examples of which include, but are not limited to: 1)essentially real-time audio and/or visual feedback to a technician(e.g., directing the mobile broadcast apparatus 130 along theneighborhood node drive path 305, or operating the portable/handheldfield device 140 in proximity to a potential point of ingress); 2) atext-based listing of one or more potential points of ingress (e.g.,providing geographic location and optionally prioritizing in some mannermultiple potential points of ingress); and 3) one or more visualrenderings comprising one or more graphs, charts, diagrams and/or mapsof various dimensions (e.g., one-, two- or three-axis renderings ofinformation), in which in some examples the neighborhood node drive pathitself may be represented (e.g., “neighborhood node ingress maps;” seeSection III.C).

Given the various types of information that may be utilized by theprocessor 120, in some embodiments the processor may process and/oranalyze one or both of the first and second records, in some cases intandem with other information, to automatically determine one or moreof: 1) one or more potential points of ingress in a given neighborhoodnode under evaluation; 2) a relative severity of the potential points ofingress (e.g., so as to prioritize prospective repair or remediationactivities in the neighborhood node under evaluation); and 3)differentiation between hardline coaxial cable plant-related faults andsubscriber-related faults (e.g., in one or more subscriber service dropsand/or subscriber premises). As noted above, any of the foregoing andother results of processing and analysis by the processor 120 may beconveyed via one or more visual renderings comprising one or moregraphs, charts, diagrams and/or maps of various dimensions (e.g., one-,two- or three-axis renderings of information), in which different visualcodes or symbols may be employed to indicate hardline cableplant-related faults and subscriber-related faults, respectively, and/orto indicate different classes/severity of multiple hardline cableplant-related faults and/or subscriber-related faults.

In some examples relating to processing and/or analysis of informationrelating to the first and/or second records, the processor 120 mayemploy geo-fencing techniques in connection with the first record so asto extract only geographic information relating to one or moreparticular positions of the mobile broadcast apparatus 130 along theneighborhood node drive path 305. In other examples, the processor 103may employ peak analysis techniques or “thresholding” in connection withone or both of the first record and the second record; in particular,the processor may compare respective signal amplitudes of the secondrecord to a threshold value to facilitate automatic detection andindication of possible faults constituting potential points of signalingress (e.g., that result in received test signal strengths in excessof the threshold value).

In other examples, the processor 120 may process information relating tothe first and/or second records based at least in part on multiplesignal amplitude values corresponding to substantially similargeographic positions along the neighborhood node drive path. Forexample, in some implementations, as the mobile broadcast apparatus 130is directed along the neighborhood node drive path 305, the mobilebroadcast apparatus may traverse a same portion of the neighborhood nodedrive path more than once (e.g., in opposite directions traveling backand forth along a road ending in a cul-de-sac). More generally, at leasta first portion of the neighborhood node drive path may include afirst-pass segment and a second-pass segment over which the mobilebroadcast apparatus 130 traverses at least a first time and a secondtime, respectively. Accordingly, the mobile broadcast apparatus may haveone or more substantially identical positions along the first-passsegment and the second-pass segment (e.g., at different times),corresponding to respective signal amplitudes in the second record(which may be the same or different). In one implementation based on theforegoing scenario, the processor 120 may process the signal amplitudesin the second record to determine an average value of the respectivesignal amplitudes corresponding to the substantially identical positionsalong the first-pass segment and the second-pass segment. In anotherimplementation, the processor 120 may process the signal amplitudes inthe second record to determine a difference value of the respectivesignal amplitudes corresponding to the substantially identical positionsalong the first-pass segment and the second-pass segment. In yet otherimplementations discussed further below, the processor may process thesignal amplitudes corresponding to substantially identical positionsalong the first-pass segment and the second-pass segment based at leastin part on adjacent signal amplitudes in a succession of signalamplitudes in the first-pass segment and the second-pass segment,respectively, proximate to the substantially identical positions (e.g.,based at least in part on the rate of change of the amplitude profile).

In other examples relating to processing and/or analysis of informationrelating to the first and/or second records, the processor 120 mayemploy analysis techniques including, but not limited to, trilateral andhyperbolic data analysis. One approach for trilateration of a potentialpoint of ingress in the cable communication system includes using therelationship between a distance of the transmitter from a faultconstituting a potential point of ingress and the signal amplitude ofthe received test signal. As this distance increases, the receivedamplitude generally decreases (by approximately the inverse square ofdistance for omni-directional transmission antennae, and by otherdeterminable relationships for directional antennae). Accordingly, aprospective fault position constituting a potential point of ingress maybe identified by using multiple known points of transmission.

More specifically, FIG. 30 illustrates variations in received testsignal amplitude as monitored by the analyzer shown in FIG. 28, based ona distance between a fault in a cable communication system and atransmitter transmitting the test signal, according to one embodiment ofthe present invention. In addition to using trilateration techniquesbased on the relationships shown in FIG. 30 to identify locations ofpotential points of ingress, the relationships shown in FIG. 30 may beemployed more generally to facilitate an analysis of the rate ofamplitude change to estimate a distance between the transmitter of thetest signal and a fault constituting a potential point of interest. Sucha determination may facilitate differentiation of a hardline cableplant-related fault (presumed to be relatively close to the neighborhoodnode drive path proximate to the hardline coaxial cable plant) and asubscriber-related fault (which in some cases, particularly relating tosubscriber premises faults, may be somewhat farther away in distancefrom the neighborhood node drive path). In general, analyzing the rateof amplitude change across a series of positions at which the testsignal is broadcast/transmitted allows the distance to a prospectivepoint of ingress from the point of closest approach and its relativereceptivity to be determined.

As illustrated in FIG. 30, the amplitude profile of a roughly lineartransmission path traversing arbitrarily near a fault constituting apoint of ingress increases to peak amplitude at a point of closestapproach more quickly (higher rate of change) the closer that lineartransmission path is to the fault. Amplitude varies logarithmically tothe inverse of the sum of the squares of distance to the fault atclosest approach and distance along the transmission path from thefault. The point of half power relative to the peak bears specialsignificance. In some implementations, this analytical technique reducesthe ambiguity of distance vs. receptivity in interpreting peakamplitude. Specifically, analyzing the rate of amplitude changeaccordingly helps distinguish a close but moderate fault from a moredistant but more serious (i.e. more receptive) fault, which faults mightbe indistinguishable if peak amplitude was analyzed in isolation. Whilea single “drive-through” or pass traversing the neighborhood node drivepath 305 may yield a mirror-image ambiguity (i.e., known distance, buttwo possible bearings, 180° apart), multiple, angularly distinct passeseffectively eliminate this ambiguity. This analytical technique is alsoapplicable to more complex transmission paths and reception scenarios.

Interferometry is another analysis technique that may be implemented asan alternative or additional method for identifying prospective pointsof ingress or fault locations. Interference patterns may occur where thetest signal impinges upon multiple faults and enters into the cablecommunication system as ingress, in which the constituent test signalcomponents entering the multiple faults may have respective differentphase relationships. The test signal components entering the respectivefaults are ultimately combined together in the cable communicationsystem. As the mobile broadcast apparatus traverses the neighborhoodnode drive path, the phase relationships corresponding to the multiplefaults change in conjunction with the (differently) changing pathdistances between the faults and the test signal transmitter, givingrise to test signal interference patterns which may be observed, forexample, by the analyzer 110. In particular, these interference patternsmay be seen in the varying amplitude readings as the mobile broadcastapparatus traverses the neighborhood node drive path, and are mostpronounced when faults are in close proximity to one another and ofsimilar receptivity.

FIG. 31 illustrates an interference pattern model, according to oneembodiment of the present invention, of test signal ingress via tworelatively widely-separated faults in a cable communication system, andFIG. 32 illustrates an interference pattern model, according to oneembodiment of the present invention, of test signal ingress via tworelatively narrowly-separated faults in a cable communication system.From FIGS. 31 and 32, it may be readily appreciated that analysis ofsuch interference patterns as represented in the plurality of signalamplitudes in the second record (i.e., the changing phase relationshipsand therefore level of constructive and destructive interference overtransmission position) provides useful information about the relativepositions of the possible faults and corresponding potential points ofingress in question. In exemplar implementations, determination ofprospective fault location via analysis based on interference patternsin signal amplitude data may be performed using a single frequency testsignal (i.e., “homodyne detection”), or multiple (typically two)frequencies (i.e., “heterodyne detection”).

In other embodiments, a processing and/or analytical technique involvinga hyperbolic approach uses the TDOA of a signal at various points ofingress, and/or from multiple transmission points, to pinpointprospective fault locations. Some advantages of this approach generallyinclude reduced vulnerability to interference patterns typicallygenerated by multiple points of ingress, as discussed above.Additionally, the hyperbolic approach does not rely on an absoluteamplitude reading, making location of low level (i.e., distant) ingresspoints potentially more accurate or sensitive.

In yet other embodiments, complex event processing (CEP) may be utilizedby the processor 120 in conjunction with processing and/or analyzingmultiple external data streams to assist in fault location, diagnosis orroot cause analysis. Examples of external data streams/sets that may beprocessed via CEP techniques according to some embodiments include,include information derived from but not limited to the followingsources: the first and second records, street maps, cable facilitiesmaps, parcel maps, aerial images, subscriber information (e.g., VIPcustomer locations or other subscriber data relating to deliveredservices), ambient noise/ingress in the frequency range of the upstreampath bandwidth, environmental data (temperature, weather, etc.), cablecommunication system design data, terrain, service ticketing systemrecords (relating to maintenance, repair, service changes/upgrades,etc.), technician locations/activity, and DOCSIS equipment status data(e.g., relating to one or more subscriber modems or demodulation tunersat the headend). For example, an indication that ingress is entering thesystem at a particular subscriber premise, combined with the knowledgethat service work (via the ticketing system) was recently performedthere, may inform the remediation (e.g., diagnosis and/or repair)process. Alternately, a presence of ingress detected in the systemcoupled with the knowledge that temperatures had recently changeddramatically, may point a technician toward a bad cable-to-connectorinterface (due to the physical contraction and expansion of the cable astemperatures change). Also, terrain data may inform a propagation modelfor locating faults based on the data collected.

In yet other embodiments, and particularly in connection with block 216of the method outlined in FIG. 29, an “expanded” third record furthermay be generated to include entries for additional geographic locationsnot included in the first record, but corresponding to geographiclocations within the general area covered by the neighborhood node underevaluation. Such additional geographic locations included in theexpanded third record, upon which a neighborhood node ingress map may begenerated as discussed further below, provide for a higher resolutionand/or increased geographical coverage for the illustrativerepresentation of ingress provided by such a map. To provide relativedegrees of ingress corresponding to these additional geographiclocations, the plurality of signal amplitudes obtained from the secondrecord may be interpolated to include estimated signal amplitudescorresponding to the additional locations in the expanded third record.In one exemplary implementation, the processor 120 may use the Gnuplotgraphing utility (e.g., see www.gnuplot.info), Wolfram's Mathematicaprogram (e.g., see www.wolfram.com/mathematical), or other similarutility (i.e., a portable command-line driven graphing utility) tointerpolate signal amplitudes corresponding to additional geographiclocations included in the expanded third record, upon which aneighborhood node ingress map may be generated according to variousembodiments. Below is an illustrative example of a routine implementedusing the Gnuplot graphing utility for accomplishing such interpolation(it should be appreciated that other methods/routines may be employed toimplement interpolation of data as discussed herein:

Syntax:

-   -   set dgrid3d {, {<row size>} {,{<col size>} {,<norm>}}}    -   set nodgrid3d

Examples:

-   -   set dgrid3d 10,10,2    -   set dgrid3d, 4

The first example selects a grid of size 10 by 10 to be constructed andthe use of L2 norm in the distance computation. The second example onlymodifies the norm to be used to L4. By default this option is disabled.When enabled, 3d data read from a file is always treaded as a scattereddata set. A grid with dimensions derived from a bounding box of thescattered data and size as specified by the row/col size above iscreated for plotting and contouring. The grid is equally spaced in x andy while the z value is computed as a weighted average of the scatteredpoints distance to the grid points. The closer the scatter points to agrid point are the more effect they have on that grid point. The third,norm, parameter controls the “meaning” of the distance, by specifyingthe distance norm. This distance computation is optimized for powers of2 norms, specifically 1, 2, 4, 8, and 16, but any nonnegative integercan be used. This dgrid3d option is a low pass filter that convertsscattered data to a grid data set. More sophisticated approaches may beemployed as a preprocess to and outside Gnuplot. For example, theShepherds inverse distance weighting algorithm (seehttp://en.wikipedia.org/wiki/Inverse distance weighting), available inMathematica, may be employed for this purpose.

C. Graphical Representations

As noted above, in connection with block 216 of the method outlined inFIG. 29 relating to phase 1 activity, various results of processing andanalysis by the processor 120 relating to a first record of geographicinformation and a second record of signal amplitudes may be conveyed viaone or more visual renderings comprising one or more graphs, charts,diagrams and/or maps of various dimensions (e.g., one-, two- orthree-axis renderings of information), in which different visual codesor symbols may be employed to indicate various types of information. Thepresentation of such information, irrespective of particular format andcontent, generally is referred to herein as “a neighborhood node ingressmap.”

In various embodiments, the processor 120 may provide informationrelating to a neighborhood node ingress map so as to render one or moremaps with visual codes for illustrating respective signal amplitudes(e.g., color; gray tone; different shading, hatching or symbols), aswell as various types of map presentations (e.g., one-dimensional,two-dimensional, three-dimensional, heat maps, modified topographicalmaps, etc.). Information provided by the processor 120 for renderinggraphical representations of ingress may be communicated by theprocessor to any one or more of the analyzer 110, mobile broadcastapparatus 130, or portable/handheld field device 140 shown in FIG. 28,and/or ingress maps may be displayed locally on the processor's displaydevice 121. In some exemplary implementations, map data may be saved andcommunicated as .png files, but it should be appreciated that a varietyof graphical formats may be employed (including formats that allow forvarious degrees of transparency in connection with overlaying multiple“layers” of map information and/or image information, such as satelliteor aerial images, street maps, cable facilities maps, parcel maps,ambient ingress maps, subscriber information, DOCSIS information, etc.,which information the processor may acquire from any of a variety ofconventional sources, via communication interface 122 and/orcommunication network 150, and/or stored in memory 126).

In some embodiments, the neighborhood node drive path 305 traversed bythe mobile broadcast apparatus 130 may itself be rendered on theneighborhood node ingress map. With respect to rendering theneighborhood node drive path if desired, the processor may acquire fromany of a variety of conventional sources (e.g., via communicationinterface 122 and/or communication network 150, and/or stored in memory126) one or more street maps for the appropriate geographic areacorresponding to the neighborhood node, and employ these as received, orfiltered/simplified to render simple line drawings of the neighborhoodnode drive path, on which are superimposed or overlaid the visual codesrepresenting relative degrees of signal ingress as a function ofposition along the drive path.

More specifically, in some embodiments of neighborhood node ingress mapsaccording to the present invention, the graphical representation for theingress map may comprise a two-dimensional representation including anyof a variety of types of street maps (or simplified versions of streetmaps to provide simple line drawings of thoroughfares) showing theneighborhood node drive path 305 traversed by the mobile broadcastapparatus 130, and a visual code for the plurality of signal amplitudesrepresenting the strength of the received upstream test signal andrelative degree of ingress at a given location superimposed or overlaidon the neighborhood node drive path. For example, an x-axis (orhorizontal coordinate scale) and a y-axis (or vertical coordinate scale)for the map respectively may represent latitude and longitude, and agiven signal amplitude corresponding to a latitude/longitude coordinatepair may be indicated with the visual code in the x-y plane of the map.In one implementation involving a “heat map,” the visual code includes acolor code, and a color of the color code represents a correspondingsignal amplitude. In another implementation, the visual code includes agray-tone scale, and a shade of gray represents a corresponding signalamplitude. In yet other implementations, examples of visual codesinclude, but are not limited to: a plurality of different hatchingstyles, wherein respective hatching styles of the plurality of differenthatching styles represent different signal amplitudes; a plurality ofdifferent shading styles, wherein respective shading styles of theplurality of different shading styles represent different signalamplitudes; and a plurality of different symbols, wherein respectivesymbols of the plurality of different symbols represent different signalamplitudes.

FIGS. 33 through 36 illustrate examples of neighborhood node ingressmaps in the form of two-dimensional “heat maps” in which the visual codefor the plurality of signal amplitudes is implemented as a color code(although these maps will appear to be rendered in a gray-tone scale inblack and white in some publications, copies of this patent publicationwith color drawing(s) will be provided by the U.S. Patent Office uponrequest and payment of the necessary fee).

More specifically, the heat maps 300A, 300B, 300C and 300D respectivelyshown in FIGS. 33 through 36 constitute a time-series of fourneighborhood node ingress maps corresponding to ingress mitigated nodeBT-11 shown in FIGS. 23 and 24, wherein each heat map of the series isgenerated pursuant to the method outlined and discussed above inconnection with FIG. 29. In tandem with generation of the time-series ofmaps 300A, 300B, 300C and 300D shown in FIGS. 33 through 36, some typeof remediation effort (i.e., repair, replacement and/or adjustment ofone or more system components) pursuant to phase 2 activity (discussedin greater detail below in Section IV) was conducted after generation ofthe heat map 300A and before generation of the heat maps 300B, and thenagain before generation of each of the heat maps 300C and 300D. Thus,the time series of four heat maps shown in FIGS. 33 through 36represents multiple iterations of phase 1 and phase 2 activity, andillustrates corresponding incremental improvements in the noise profile(i.e., incremental and significant reductions in ingress) in the ingressmitigated node BT-11 pursuant to each iteration of phase 1 and phase 2activity.

In the illustrated embodiments, each of the heat maps 300A, 300B, 300Cand 300D includes a first graphical representation of the neighborhoodnode drive path 305 traversed by the mobile broadcast apparatus 130,together with a second graphical representation of the plurality ofsignal amplitudes representing locations of potential points of ingressin the neighborhood node, based on a color-coded scale for a relativedegree of ingress as a function of geographic location. In particular,the x-axis or horizontal axis of each of the heat maps 300A, 300B, 300Cand 300D represents latitude coordinates in degrees, the y-axis orvertical axis represents longitude coordinates in degrees, and a colorlegend 303 indicates a correspondence between colors represented in theheat map and a relative level of ingress, as represented by signalamplitudes representing strengths of an upstream test signal received atthe headend of the cable communication system (e.g., black≈−90 dBmV;blue≈−80 to −70 dBmV; violet≈−60 dBmV; red≈−50 dBmV; red-orange≈−40dBmV; orange≈−30 dBmV; orange-yellow≈−20 to −10 dBmV; yellow≈0 dBmV).While the heat maps 300A, 300B, 300C and 300D illustrated in FIGS. 33through 36 use an essentially continuous color scale for the colorlegend 303, it should be appreciated that a discrete color scalesimilarly may be employed, of various resolutions.

FIG. 37 illustrates a heat map 300E similar to the map shown in FIG. 33,on which are indicated potential points of signal ingress, according toone embodiment of the present invention. In some embodiments, asillustrated in FIG. 37, potential points of ingress may be indicated bycircles 302 denoting specific areas at which relatively strong signalamplitudes of a broadcast test signal were received (e.g., by theanalyzer 110), based on the color-coded legend. Although circles 302 areemployed in FIG. 37 to indicate potential points of ingress on the headmap 300E, it should be appreciated that any of a variety of symbols,marks, shapes colors or other indicators may be employed in variousembodiments so as denote potential points of ingress. The circles 302 orother indicators may in some implementations be added manually to theheat maps following a visual inspection (e.g., via a user interface of acomputing device such as the processor 102, or mobile broadcastapparatus and/or the portable/handheld field device); in otherimplementations, peak analysis with respect to some threshold value maybe performed (e.g., as discussed above in Section III.B) in connectionwith the plurality of signal amplitudes in the second record so as toautomatically generate and provide on the heat map circles 302 (or otherindicators) to denote significant signal strengths indicating potentialingress.

In other embodiments, the graphical representation for a neighborhoodnode ingress map may be in the form of a modified topographical map, inwhich contour lines are employed to reflect signal amplitude rather thanelevation. To this end, FIG. 38 illustrates another example of aneighborhood node ingress map in the form of a modified topographicalmap, or contour map 400, in which contour lines (and optionallydifferent shadings within an area bounded by a contour line) areemployed to signify signal strength. In another example, theneighborhood node ingress map may be in the form of a one-dimensionalmap 402, as shown in FIG. 39, illustrating signal amplitude (e.g., alonga vertical or y-axis) as a function of time or position (e.g., along ahorizontal or x-axis) along at least a portion of the neighborhood nodedrive path 305. In yet another example, the neighborhood node ingressmap may be in the form of a three-dimensional map 404, as shown in FIG.40, in which the signal amplitudes 406 may be plotted along a z-axis,and a heat map 300 for at least a portion of the ingress mitigated nodeBT-11 also is illustrated in the x-y plane to provide another type ofvisualization for ingress in the cable communication system. In FIG. 40,the three-dimensional map 404 also includes an aerial image layer 408which, as discussed in greater detail below, may be included as one ofmultiple layers in an ingress “overlay” map (discussed further below).In various aspects, in a manner similar to two-dimensionalrepresentations, color, gray-scale, or other types of visual codes alsomay be employed in connection with a one-dimensional orthree-dimensional graphical representation. Thus, it should beappreciated that various examples of neighborhood node ingress maps areprovided in the accompanying figures primarily for purposes ofillustration, and that a variety of graphical representations may beemployed to render neighborhood node ingress maps according to variousembodiments of the present invention.

From both FIGS. 39 and 40, a profile of the plurality of signalamplitudes may be more clearly observed as a function of distancetraversed along at least a portion of the neighborhood node drive path305 (and similarly as a function of time). As discussed above in SectionIII.B, the signal amplitudes may in some embodiments be processed and/oranalyzed (e.g., by the processor 120), so as to adduce variousinformation relevant to identification of possible faults constitutingpotential points of ingress. For example, the magnitude of respectivepeaks in the profile of signal amplitudes may suggest particular typesof faults, as well as respective positions of different peaks relativeto one another (e.g., resulting from constructive/destructiveinterference of the test signal entering into multiple faults), and/ordifferent rates of change in the signal amplitude associated with one ormore peaks (e.g., which manifest as different peak heights and/ordifferent widths of peak waveforms). As discussed above and illustratedin connection with FIGS. 30, 31 and 32, interference patterns resultingfrom a test signal entering into multiple faults, and/or differentamplitude profiles resulting from respective distances between thetransmitter of the test signal and a given fault, provide significantand useful information that may facilitate fault identification. In someimplementations, mere observation of such amplitude profiles by atrained/experienced technician, with or without the aid of signalprocessing enabled by the processor 102, may reveal valuable empiricalinsights into the nature and/or location of various possible faults.

In yet other embodiments, the processor 120 may provide informationrelating to a neighborhood node ingress map so as to render one or moremaps as ingress “overlay” maps, in which one or more representations ofinformation are overlaid on one or more other representations ofinformation. In one aspect, respective layers of an ingress overlay lapmay be independently selectable and/or independently viewable layers soas to facilitate comparative viewing of the information represented inthe respective layers, and in some instances manipulation of information(e.g., pan, zoom, color/graytone options, crop, etc.) to facilitateenhanced viewing. As noted above, the processor 120 may utilize avariety of information, examples of which include but are not limitedto, the first and second records, satellite or aerial images, streetmaps, cable facilities maps, parcel maps, ambient ingress maps,environmental information (e.g., weather, terrain), various subscriberinformation, and various DOCSIS information (which information theprocessor may acquire from any of a variety of sources via communicationinterface 122 and/or communication network 150, and/or stored in memory126). As noted above, information provided by the processor 120 forrendering graphical representations of ingress overlay maps may becommunicated by the processor to any one or more of the analyzer 110,mobile broadcast apparatus 130, or portable/handheld field device 140shown in FIG. 28, and/or ingress overlay maps may be displayed locallyon the processor's display device 121.

More generally, any one or more layers of information that mayconstitute one or more layers of a neighborhood node ingress map in theform of an ingress overlay map may be in the form of an “input image”that may be represented by source data that is electronically processed(e.g., the source data is in a computer-readable format) to display theimage on a display device. An input image may include any of a varietyof paper/tangible image sources that are scanned (e.g., via anelectronic scanner) or otherwise converted so as to create source data(e.g., in various formats such as XML, PDF, JPG, BMP, etc.) that can beprocessed to display the input image. An input image also may include animage that originates as source data or an electronic file withoutnecessarily having a corresponding paper/tangible copy of the image(e.g., an image of a “real-world” scene acquired by a digital stillframe or video camera or other image acquisition device, in which thesource data, at least in part, represents pixel information from theimage acquisition device).

In some exemplary implementations, an input image may be created,provided, and/or processed by a geographic information system (GIS) thatcaptures, stores, analyzes, manages and presents data referring to (orlinked to) location, such that the source data representing the inputimage includes pixel information from an image acquisition device(corresponding to an acquired “real world” scene or representationthereof), and/or spatial/geographic information (“geo-encodedinformation”). In view of the foregoing, various examples of inputimages that may constitute at least a portion of a neighborhood nodeingress map, and source data representing such input images, include butare not limited to:

Manual “free-hand” paper sketches of the geographic area (which mayinclude one or more buildings, natural or man-made landmarks, propertyboundaries, streets/intersections, public works or facilities such asstreet lighting, signage, fire hydrants, mail boxes, parking meters,etc.);

Various maps indicating surface features and/or extents of geographicalareas, such as street/road maps, topographical maps, military maps,parcel maps, tax maps, town and county planning maps, call-center and/orfacility polygon maps, virtual maps, etc. (such maps may or may notinclude geo-encoded information);

Facility maps illustrating installed underground facilities, such asgas, power, telephone, cable, fiber optics, water, sewer, drainage, etc.Facility maps may also indicate street-level features (streets,buildings, public facilities, etc.) in relation to the depictedunderground facilities. Examples of facility maps include CAD drawingsthat may be created and viewed with a GIS to include geo-encodedinformation (e.g., metadata) that provides location information (e.g.,infrastructure vectors) for represented items on the facility map;

Architectural, construction and/or engineering drawings and virtualrenditions of a space/geographic area (including “as built” orpost-construction drawings);

Land surveys, i.e., plots produced at ground level using references toknown points such as the center line of a street to plot the metes andbounds and related location data regarding a building, parcel, utility,roadway, or other object or installation;

A grid (a pattern of horizontal and vertical lines used as a reference)to provide representational geographic information (which may be used“as is” for an input image or as an overlay for an acquired “real world”scene, drawing, map, etc.);

“Bare” data representing geo-encoded information (geographical datapoints) and not necessarily derived from an acquired/captured real-worldscene (e.g., not pixel information from a digital camera or otherdigital image acquisition device). Such “bare” data may be nonethelessused to construct a displayed input image, and may be in any of avariety of computer-readable formats, including XML); and

Photographic renderings/images, including street level, topographical,satellite, and aerial photographic renderings/images, any of which maybe updated periodically to capture changes in a given geographic areaover time (e.g., seasonal changes such as foliage density, which mayvariably impact the ability to see some aspects of the image).

It should also be appreciated that source data representing an inputimage may be compiled from multiple data/information sources; forexample, any two or more of the examples provided above for input imagesand source data representing input images, or any two or more other datasources, can provide information that can be combined or integrated toform source data that is electronically processed to display an image ona display device.

In various embodiments, respective layers of a neighborhood node ingressmap may be displayed side by side with one or more input images, oralternatively may be overlaid on one another (e.g., via appropriatecorrelation/registration of a geographic coordinate reference frame usedfor geographic coding of the ingress map and input image(s)). In oneaspect, the respective layers may be selectively enabled or disabled fordisplay (via a user interface associated with a display device) tofacilitate comparative overlaid viewing with one another. In particular,in one implementation, with reference again to the ingress detectionsystem 100 shown in FIG. 28, any one or more of the display device(s)111, 121, 131, and 145 may be controlled to display an ingress overlaymap including multiple information layers. In one aspect, the technicianmay employ a user interface in any one of the analyzer 110, processor120, mobile broadcast apparatus 130, or portable/handheld field device140 to select display layers for viewing, and adjust the scale,resolution and/or position of the displayed ingress overlay map.

FIG. 41 illustrates a first ingress overlay map 320A serving as aneighborhood node ingress map, in which the heat map 300A of FIG. 33 isoverlaid on the cable facilities map 310 of FIG. 24. In FIG. 41, acenter portion 325A of the map 320A is indicated, which is in turn shownexpanded and with greater resolution in FIG. 42. In general, via thevisual aid of such an ingress overlay map in which a cable facilitiesmap 310 is used as a constituent layer, a field technician may readilyidentify ingress trouble spots in the hardline coaxial cable plant,target specific areas/elements of the hardline cable plant for furtherinvestigation, and target specific components of the hardline cableplant for repair, replacement or adjustment. In some implementations, asdiscussed above in Section III.B, processing/analysis of the firstrecord of geographic information and the second record of signalamplitudes (e.g., thresholding of amplitude peaks, analysis of rate ofchange of amplitudes), in some instances together with additionalinformation (e.g., metadata from the cable facility map 310), providesfor automated indications on the ingress overlay map 320A of possiblefaults constituting potential points of ingress. Accordingly, one orboth of the visual aid provided by heat map overlaid on a cablefacilities map, and automated indications of possible faults, provide avaluable tool to facilitate remediation of faults.

From FIG. 42, it may be readily observed from the expanded portion 325Aof the ingress overlay map 320A that a region of high signal amplitude(appearing in a yellow-orange color in the heat map 300A) indicatedalong an uppermost vertical portion of the neighborhood node drive path305 (“Mountain Oaks Dr.”) suggests one or more faults. Morespecifically, FIG. 42 includes a first indicator 1800A (e.g., a“lightning bolt” with the letter “H”) to indicate a first possible faultin the hardline coaxial cable plant (in which a nearby tap 188 isindicated in the underlying cable facilities map 310), and a secondindicator 1800B to indicate a second possible fault in the hardlinecoaxial cable plant. FIG. 42 also indicates an information table 307 inconnection with the first possible fault (the nearby tap 188), showingvarious information regarding the component suspected of being faulty(an identification for the tap, number of ports, attenuation value,hardline cable diameter to which the tap is coupled, etc.). Such aninformation table 307 may be provided for one or more faults indicatedon the ingress overlay map 320A; for example, while not shown explicitlyin FIG. 42, the second indicator 1800A may be associated with a lengthof hardline coaxial cable suspected as being faulty, and an informationtable in connection with same may indicate a plant location ID for thecable, a cable diameter, and part numbers/ID for the nearest active orpassive components. In some implementations, a “scroll-over” of the areaproximate to a fault indicator may cause such an information table 307to be displayed).

FIG. 43 illustrates a parcel map 315 corresponding to the ingressmitigated node BT-11 shown in FIGS. 41 and 42, which parcel map also maybe utilized as a layer in an ingress overlay map serving as aneighborhood node ingress map according to one embodiment of theinvention. To this end, FIG. 44 illustrates another example of aneighborhood node ingress map in the form of an ingress overlay map320B, in which the heat map 300A of FIG. 33 is overlaid on the parcelmap 315 of FIG. 43. In FIG. 44, a center portion 325B of the map 320B isindicated, which is in turn shown expanded and with greater resolutionin FIG. 45. In various embodiments, information contained in the parcelmap 315 relating to the households passed by hardline cable plant (andthe neighborhood node drive path), and the metes/bounds of same, mayfacilitate identification of possible subscriber-related faults, anddifferentiation between hardline cable plant-related faults andsubscriber-related faults. In particular, by combining information froma heat map, a parcel map, and various subscriber information (e.g.,provided by the cable communication system operator), subscriber-relatedfaults vis a vis hardline cable plant-related faults may be more readilyidentified. In FIG. 45, a subscriber-related fault indicator 1850 (e.g.,a “lightning bolt” with the letter “S”) is provided to indicate apotentially problematic subscriber premises and/or subscriber drop. FIG.45 also indicates an information table 307 in connection with thesuspected subscriber-related fault, similar to that shown in FIG. 43,providing various information regarding the associated subscriber(address, data services package, tap attenuation value, length of dropcable, any special status such as VIP subscriber, hospital, school,military, government, etc.).

Thus, ingress overlay maps involving one or both of a cable facilitiesmap 310 and a parcel map 315 may include various information relating torespective elements of the hardline coaxial cable plant and/orsubscriber premises in the neighborhood node displayed on the ingressoverlay map. With respect to elements of the hardline coaxial cableplant, such information may include system design information relevantto respective components (e.g., location ID number, model number,standard operating levels, date and purpose of last visit by atechnician, subscriber counts/addresses for taps, etc.). With respect tosubscriber premises, an ingress overlay map including a parcel map mayfurther display for one or more subscriber premises the associatedaccount information (e.g., phone number, address, service plan type,number/type of outlets, date purpose and resolution codes of lastservice call, VIP or other special status etc.).

FIG. 46 illustrates another example of a neighborhood node ingress mapin the form of an ingress overlay map 320C, in which the heat map 300Aof FIG. 33 is overlaid on an aerial image (e.g., obtained from GoogleEarth), according to one embodiment of the present invention. In oneimplementation, registration of the heat map 300A on the aerial imagemay be accomplished by calculating the maximum north, south, east, andwest values of the bounding drive path from the ingress map to determinethe appropriate metes and bounds of the satellite/aerial image. In FIG.46, a center portion 325C of the map 320C is indicated, which is in turnshown expanded and with greater resolution in FIG. 47. In a mannersimilar to the cable facilities map 310 and the parcel map 315, ingressoverlay map 320C including an aerial image that shows various terrainfeatures as well as the footprint of the neighborhood node drive path305 and premises within the neighborhood may facilitate identificationof one or more hardline cable plant-related faults and/or one or moresubscriber-related faults. For example, in the portion 325C of theingress overlay map 320C, FIG. 47 illustrates first and second hardlinecable plant fault indicators 1800A and 1800B, as well assubscriber-related fault indicator 1850, so as to facilitatedifferentiation between possible hardline cable plant-related faults andsubscriber-related faults. It should be appreciated that such faultindicators for hardline cable plant-related faults andsubscriber-related faults, respectively (which may include any of avariety of codes or symbols) may be employed with “single layer”neighborhood node ingress maps (e.g., heat maps, contour maps, maps ofvarious dimensions, etc.) as well as different types of ingress overlaymaps serving as a neighborhood node ingress map according to variousembodiments.

For example, in accordance with various embodiments, information such ascustomer VIP lists, environmental data, terrain maps, technicianactivity/location, or DOCSIS status reporting, could be incorporatedinto a visual rendering or graphical representation constituting part ofa neighborhood node ingress map, as one or more separate layers and/orselectable elements of one or more layers. In some implementations,display of such information may include, but is not limited to:“push-pins” or other markers to indicate the location of business or VIPcustomers, since service interruption protocols for plant correctiveaction may differ for these customers (e.g., there may be notificationrequirements, restricted time-of-day service windows, etc.); current orhistorical weather data tied to the ingress mapping may elucidateintermittent problems related to environmental conditions such as rainor cold temperatures, or other significant weather conditions that maybear upon different cable communication system elements and particularlythe hardline coaxial cable plant; knowledge of recent or concurrentactivity by other technicians may further inform the troubleshooting orrepair process.

IV. PHASE 2—LOCAL INGRESS VERIFICATION AND REMEDIATION

In phase 2 of a two-phase implementation of an ingress detection andremediation method according to one embodiment of the present invention,specific locations of ingress in a neighborhood node under evaluationare verified, and system components in the neighborhood node that aredirectly responsible for ingress (particularly in the hardline coaxialcable plant) are specifically identified, isolated, and repaired,replaced or adjusted if/as necessary. In particular, based on one ormore neighborhood node ingress maps generated in phase 1, a fieldtechnician may proceed to one or more particular locations in theneighborhood node where the map(s) indicate potential points of signalingress, and employ a portable (e.g., handheld) field device 140 as atest instrument, as discussed above (see FIG. 28), to specificallyidentify potential ingress points by traversing a target ingress problemarea with greater geographical resolution (e.g., on foot, by bicycle,via a small motorized or non-motorized vehicle, etc.).

In some embodiments of phase 2 activity, a field technician may firstproceed to a target ingress problem area in a vehicle traversing someportion of the neighborhood node under evaluation. During such aninitial “drive out” en route to a target ingress problem area,geographic information from the first record and signal amplitudes fromthe second record generated during phase 1 activity may be used toprovide to the field technician one or more indications in the vehicle(e.g., audible and/or visual indications) of signal strength as measuredand recorded during phase 1 at various positions along the neighborhoodnode drive path; in essence, the original phase 1 drive-through may be“replayed” in some fashion to the field technician so as to provideindicators (e.g., audible and/or visual warnings) to the technician asthe vehicle approaches areas where significant signal amplitudes weremeasured during phase 1 activity. In one implementation, a firstneighborhood node ingress map generated during phase 1 activity may bedisplayed on a display screen in the vehicle, in which a geo-marker forthe vehicle location during phase 2 “drive-outs” is superimposed on theingress map (to provide the technician with a “you are here” indicator).

FIG. 48 outlines phase 2 of an exemplary ingress detection andremediation method according to one embodiment of the present invention.At block 218, one or more local test signals is/are transmitted, at orproximate to at least one potential point of the signal ingress, in anupstream path bandwidth of the neighborhood node under evaluation. Forexample, with reference again to FIG. 28, portable or handheld device140 including a transmitter 143 may be used by a field technician sentto investigate potential points of ingress that were identified on themap generated by processor 120 in phase 1, discussed above (i.e., thetechnician may determine the potential point of the signal ingress via aneighborhood node ingress map generated in phase 1, and may also consulta cable communication system facilities map illustrating at least aportion of an infrastructure of the at least one neighborhood node ofthe cable communication system, if not included as part of theneighborhood node ingress map). The transmitter of the portable orhandheld device (or an independent transmitter employed by thetechnician) may be directed by the technician so as to “sweep” acrossand/or along and sufficiently proximate to an identified possible faultconstituting the potential point of ingress while generating one or morelocal test signals, which signal(s) is/are transmitted in the upstreampath bandwidth via the fault.

As in phase 1, in one aspect the local test signal(s) is/are transmittedwithout significantly interfering with operative signaling in theupstream path bandwidth from one or more subscriber premises of theneighborhood node under evaluation (e.g., via an “unused” frequency inthe upstream path bandwidth, modulation such as spread spectrum, TDM,pulse signal, etc.). More specifically, any of the techniques discussedabove in Section III.A relating to the transmission of test signalsduring phase 2 activity may apply similarly to the transmission of oneor more local test signals during phase 2 activity.

At block 220, signal amplitudes representing a strength of a receivedupstream local test signal at a headend of the cable communicationsystem, based on the transmitted local test signal in block 218, arereceived at or proximate to the at least one potential point of thesignal ingress (e.g., by the portable or handheld field device employedby the technician) as the technician traverses (e.g., walks around) thetarget ingress problem area. More specifically, a signal receiver oranalyzer (e.g., see the analyzer 110 in FIG. 28) at the headend monitorsthe upstream path bandwidth of the neighborhood node under evaluationand records signal amplitudes corresponding to received upstream localtest signals (if any). These amplitudes are then conveyed in essentiallyreal time to the field technician to provide feedback on the degree ofingress present within the target problem area.

In one example, a base technician at the headend 162 communicates (e.g.,via two-way radio, cell phone, text message, email, etc.) the receivedsignal amplitudes to the field technician to provide feedback on thereceived signal strength as the field technician traverses the targetproblem area. In another example, a signal receiver (the analyzer 110 atthe headend) includes a communication interface communicatively coupledto the portable or handheld field device 140 (e.g., via thecommunication network 150) so that the device 140 may receive signalamplitude readings via any known communication method in essentiallyreal time. This information can in turn be conveyed by the device 140(e.g., audibly, visually or both) to the field technician to provideessentially real time feedback.

More specifically, in one embodiment, the signal receiver includes acommunication interface communicatively coupled to the Internet, and thefield device 140 remotely accesses the signal receiver, via theInternet, so as to receive the signal amplitudes representing thestrength of the received upstream test signal at the headend of thecable communication system. As discussed above in connection with FIG.28, the field device 140 may include a display device to display one ormore indications corresponding to the received signal amplitudes (e.g.,a numeric display, a bar graph, a simulated meter, etc.). Alternatively,the field device 140 may include a telecommunications device thatcommunicates with the analyzer/headend via a telecommunications link(e.g., serving as the communication network 150).

In another aspect of block 220 of the method outlined in FIG. 48, theneighborhood node ingress map generated in phase 1 (which may include aningress overlay map constituted in part by a cable facilities mapillustrating cable communication system infrastructure—e.g., see FIGS.41 and 42), may be displayed locally to the field technician (e.g., viathe display device of the portable or handheld field device 140). Inthis manner, with reference to the cable facilities map layer showinghardline coaxial cable plant infrastructure and component details in theneighborhood node under evaluation, the field technician mayspecifically identify the faulty/defective component(s) of the hardlinecoaxial cable plant that is/are responsible for ingress in theneighborhood node.

In yet another aspect, the CPU(s) 144 further may control the displaydevice(s) 145 of the field device 140 to also display for the technicianone or more of the ingress map generated in phase 1, and one or moreother maps or images corresponding to the geographic area covered by theingress map, so as to facilitate an orientation of the ingress profileto the environmental surroundings and/or the hardline coaxial cableplant infrastructure. In some implementations, visualizations employingaugmented reality may be used, such that as the technician points thefield device 140 in various directions, the CPU(s) 144 and display 145may operate to overlay real-time or historical information onto a videofeed taken by an onboard camera of the field device 140 (the CPU(s) 144and display 145 may be an integral part of the field device 140 or asmart phone or similar device docked to the field device 140). Theinformation overlaid onto the scene could include RF amplitude (i.e.,field strength) data, relating to ingress, egress, ambient RF, etc.Additionally, system elements brought into view may include systemdesign information relevant to them, such as location ID number, modelnumber, operating levels, date and purpose of last visit by atechnician, subscriber counts/addresses (i.e., for taps), etc.Subscriber premises viewed in this way may have the associatedsubscriber information displayed, such as phone number, number/type ofoutlets, date purpose and resolution codes of last service call, etc.

At block 222 of FIG. 48, one or more specific elements in the hardlinecoaxial cable plant responsible for the signal ingress (e.g., faultycable or components) are identified based on the monitored changes inamplitude of the received upstream signal; that is, based at least inpart on the locally received signal amplitudes, one or more faulty ordefective infrastructure elements of the hardline coaxial cable plantmay be identified. Thereafter, the field technician may appropriatelyspecifically inspect and remediate (e.g., repair, replace or adjust)if/as necessary each of the identified faults so as to significantlyreduce or essentially eliminate ingress. To conclude phase 2, the fieldtechnician may employ the portable or handheld field device 140 toprovide verification that a remediation effort (e.g., repair,replacement, or adjustment) to mitigate ingress was effective byre-transmitting the local test signal(s) following the remediationeffort and noting a significantly attenuated signal amplitudecorresponding to the local test signal(s) received at the headend 162(e.g., a reduction on the order of 3 dB to 6 dB).

As discussed above, any of a variety of components of the hardlinecoaxial cable plant may be faulty and give rise to ingress, and duringphase 2 any one or more components of the hardline cable plant may besuccessfully identified and remediated to significantly reduce ingress.Examples of faults in the hardline cable plant that may be remediatedduring phase 2 activity include, but are not limited to, loose ordefective fittings/connectors (e.g., splice connectors, pin-typeconnectors such as housing terminators, extension fittings, 90 degreefittings, splice blocks, any of which may be loose, water-logged,corroded or otherwise damaged for example), hardline coaxial cable flaws(compromised shielding and/or broken conductors arising fromenvironmental damage, defective cable, poor craftsmanship duringinstallation, aging, squirrel chews, bullet holes, etc.), and acompromised RF ground in one or more active or passive components of thehardline cable plant (e.g., amplifiers, filters, distribution taps, lineterminators, directional couplers, etc.). Of course, beyond detectionand remediation of faults in the hardline coaxial cable plant of a givenneighborhood node, one or more subscriber-related faults (e.g., looseconnectors between the subscriber service drop and tap, pinched orotherwise compromised subscriber drop, ground block and/or internalsubscriber premises wiring and/or equipment problems, etc.) additionallyor alternatively may be detected and remediated as part of phase 1 andphase 2 activity.

FIGS. 49A through 49L illustrate expanded close-up views of facilitiesmaps showing cable communication system infrastructure, correspondingheat maps before ingress remediation, and corresponding heat maps afteringress remediation, respectively, according to various embodiments ofthe present invention. In particular, FIGS. 49A, 49D, 49G, and 49Jillustrate respective close-up portions of a cable facilities map 310showing faulty cable communication system components, FIGS. 49B, 49E,49H, and 49K illustrate corresponding respective portions of heat maps300 before remediation, and FIGS. 49C, 49F, 49I, and 49L illustratecorresponding respective portions of heat maps 300 following repair ofthe component. The series of FIGS. 49A, 49B and 49C depict a looseconnector and repair of same; likewise, the series of FIGS. 49D, 49E,and 49F also depict a loose connector and repair of same. The series ofFIGS. 49G, 49H and 49I depict a water logged connector and repair ofsame, and the series of FIGS. 49J, 49K and 49L similarly depict a waterlogged connector and repair of same.

In yet other embodiments, multiple iterations of phase 1 and phase 2activity may be performed to ensure the efficacy of ingress mitigationmethods involving detection and remediation (e.g., refer again to the“time-series” of heat maps shown in FIGS. 33-36). In particular, in someembodiments an iterative approach is adopted in which identification ofpotential points of ingress in a given neighborhood node andcorresponding remediation of hardline plant-related and/orsubscriber-related faults are conducted successively and multiple timesto document a progression of ingress mitigation efforts in a givenneighborhood node. More specifically, the Inventors have recognized andappreciated that: 1) as faults allowing for more significant ingress areremediated, “lesser” faults that allow for relatively lower (butnonetheless potentially problematic) levels of ingress may become moreevident during iterative phase 1 and phase 2 activity; and 2) somefaults may be intermittent (e.g., time-dependent and/orweather-dependent), and may be identifiable only via iterative phase 1and phase 2 activity (e.g., over different time periods and/or weatherconditions, and/or using different test signal frequencies) to identifypotential points of ingress.

In view of the foregoing, in one embodiment, after collection ofinformation during a first iteration of phase 1 activity in a givenneighborhood node, and after a first iteration of phase 2 activity inthe neighborhood node, an ingress mitigation method comprises conductingat least a second iteration of phase 1 activity in the neighborhoodnode. In one example implementation of this embodiment, a neighborhoodnode ingress map is generated as part of the first iteration of phase 1activity, and a second iteration of the neighborhood node ingress map isgenerated as part of the second iteration of the phase 1 activity, so asto ascertain an effectiveness of the first remediation. In anotheraspect, the neighborhood node ingress map and the second iteration ofthe neighborhood node ingress map may be generated as an electronicvisual rendering having a plurality of independently selectable andindependently viewable layers comprising a first layer corresponding tothe neighborhood node ingress map and a second layer corresponding tothe second iteration of the neighborhood node ingress map, so as tofacilitate comparative viewing of the respective layers. In yet anotheraspect, a second iteration of phase 2 activity is conducted in theneighborhood node (a second remediation of one or more additionalhardline plant-related and/or subscriber-related faults based on thesecond iteration of phase 1 activity) and, after the second remediation,the ingress mitigation method comprises conducting at least a thirditeration of phase 1 activity in the neighborhood node. In yet anotheraspect, a third iteration of the neighborhood node ingress map isgenerated pursuant to the third iteration of phase 1 activity so as toprovide a time series of at least three neighborhood node ingress maps.

The cumulative effect of the iterative approach as outlined above, inwhich various components of the hardline coaxial cable plant and/orsubscriber service drops or subscriber premises equipment aresuccessively repaired or replaced, leads to a dramatic reduction ofingress in a given neighborhood node across the upstream path bandwidth,with a particularly noteworthy reduction in narrowband interference inthe portion of the upstream path bandwidth between approximately 5 MHzand approximately 20 MHz (and particularly between 5 MHz toapproximately 18 MHz, and more particularly between 5 MHz andapproximately 16.4 MHz, and more particularly between 5 MHz andapproximately 10 MHz). In some implementations, even a single iterationof phase 1 activity and phase 2 activity (in various possible modes ofexecution) results in a significant reduction of ingress in a givenneighborhood node. Thus, ingress mitigation methods according to variousembodiments of the present invention effectively recover valuablebandwidth, widely recognized as being otherwise effectively unusable, toinstead be more productively and reliably employed to facilitateincreased upstream capacity for supporting voice and/or data services.

For example, with respect to various figures of merit, in variousimplementations one or more faults in the hardline coaxial cable plantof a given neighborhood node may be repaired or replaced such that ahighest value for an average noise power in at least a portion of theupstream path bandwidth below approximately 20 MHz (e.g., as measuredover at least a 24 hour period at the headend) is less thanapproximately 20 decibels (dB) (and more particularly less than 15 dB,and more particularly less than 10 dB, and more particularly less than 8dB) above a noise floor associated with the upstream path bandwidthbelow 20 MHz (e.g., as measured at the headend over the same timeperiod). In other implementations, one or more faults in the hardlinecoaxial cable plant may be repaired or replaced such that a highestvalue for the average noise power in at least a portion of the upstreampath bandwidth below approximately 20 MHz (e.g., as measured over atleast a 24 hour period at the headend) is at least 22 decibels (dB) (andmore particularly at least 24 dB, and more particularly at least 27 dB,and more particularly at least 30 dB, and more particularly at least 33dB, and more particularly at least 36 dB, and more particularly at least38 dB) below an average channel power of one or more physicalcommunication channels having a carrier frequency in the portion of theupstream path bandwidth below approximately 20 MHz and carrying upstreaminformation from one or more subscriber premises in the neighborhoodnode.

In yet other implementations, one or more faults in the hardline coaxialcable plant may be repaired or replaced so as to achieve acarrier-to-noise-plus-interference ratio (CNIR) of at least 25 decibels(dB) (and more particularly at least 28 dB, and more particularly atleast 31 dB, and more particularly at least 34 dB, and more particularlyat least 37 dB) associated with one or more physical communicationchannels deployed in the upstream path bandwidth of the neighborhoodnode (and, more specifically, channels deployed in a portion of theupstream path bandwidth below approximately 19.6 MHz, and moreparticularly below approximately 18 MHz, and more particularly belowapproximately 16.4 MHz, and more particularly below approximately 10MHz). In yet other implementations, one or more faults in the hardlinecoaxial cable plant may be repaired or replaced so as to achieve anunequalized modulation error ratio (MER) of at least 17 decibels (dB)(and more particularly at least 20 dB, and more particularly at least 22dB, and more particularly at least 24 dB, and more particularly at least28 dB, and more particularly at least 30 dB) associated with one or morephysical communication channels deployed in the upstream path bandwidthof the neighborhood node (and, more specifically, channels deployed in aportion of the upstream path bandwidth below approximately 19.6 MHz, andmore particularly below approximately 18 MHz, and more particularlybelow approximately 16.4 MHz, and more particularly below approximately10 MHz). In yet other implementations, one or more faults in thehardline coaxial cable plant may be repaired or replaced so as tosignificantly reduce a noise power (e.g., as measured at the headend)associated with one or more narrowband substantially persistent ingresssignals (e.g., short wave radio signals) constituting at least part ofthe neighborhood node ingress. Again, these results are significant,unexpected, and surprising, particularly given the cable communicationindustry's previously undisputed presumption that the portion of theupstream path bandwidth below approximately 20 MHz purportedly suffersfrom an irreparable presence of ingress.

V. OTHER CONSIDERATIONS FOR INGRESS MITIGATION

It should be appreciated that while the methods outlined in FIGS. 29 and48 provide exemplary processes for managing an ingress detection andremediation operation according to embodiments of the present invention,the underlying functionalities encompassed by these methods may beperformed by any of the various entities shown in FIG. 28 and associatedwith the ingress mitigation (e.g., detection and remediation) operation.

More specifically, it should be appreciated that, in variousembodiments, the parties performing phase 1 activity and phase 2activity, respectively, need not necessarily be the same parties, andmay or may not be under the jurisdiction/direction of a common entity.For example, in one implementation, a first party who conducts phase 1detection activity may provide one or more work orders (which may or maynot include one or more neighborhood node ingress maps) to a secondparty who is commissioned to conduct phase 2 remediation activity, afterwhich the second party reports back to the first party regarding workperformed in the field. In other embodiments, differenttechnicians/crews may attend to various elements of phase 1 and phase 2activity under the direction of a common supervising entity. In yetother embodiments, two distinct phases of activity are not necessarilyrequired to accomplish ingress mitigation; for example, one or moreelements of phase 1 activity as described herein, and one or moreelements of phase 2 activity as described herein, may be combined in aseries of tasks performed by a single crew/technician, during one ormore dispatches to the field, to effective accomplish ingress mitigationin one or more neighborhood nodes of a cable communication system.

In some embodiments, a “command center” may be employed for systemmonitoring, crew management, work planning and review of current orhistorical data. In one implementation, the processor 120 shown in thesystem 100 of FIG. 28 may be configured to serve as such a commandcenter. A command center visualization may incorporate one or more ofthe layers detailed above, but from the point of view of the entiresystem, as opposed to the activities of a one or more technicians orcrews. For example, the locations and status of all technicians might bedisplayable on any one or more of the various maps and images discussedherein. The emphasis in the command center generally is focused ondisplaying current/historical data sets, rather than guiding orinforming the collection or repair process.

In yet other embodiments of the present invention, ingress assessmentsmay be made during the course of a technician's normal fulfillment task(e.g., install, service change, disconnect, etc.). For example, at theend of such work as part of the closeout procedure for the job, a testsignal may be transmitted to test for points of ingress in the immediatevicinity (i.e., the subscriber premises). The results of this test mayinform the activities during the execution of the task at hand. As apost-test, a positive result may be used as a pre-requisite for closingthe ticket, as well as a tangible, verifiable record of theworkmanship/craftsmanship, and therefore as a potential defense againstback charges (a common liability in contract fulfillment work).

In yet other embodiments, process guides may be provided for differentfield-based usage modes (i.e., active and passive data collection,ingress mitigation/repair and fulfillment) to lead technicians throughthe various steps of the task (e.g., pursuant to phase 1 and phase 2activity) that must be completed to permit data collection or processingin connection with the relevant ingress detection modality being used.For example, a technician might be prompted to satisfy notificationrequirements before taking down the system to affect a repair. Oneaspect of this guide may include the presentation of turn-by-turnrouting instructions to a technician. This may assist during active datacollection, for example, by keeping the neighborhood node drive pathwithin test area boundaries (e.g., the neighborhood node), ensuring fullcoverage of the test area (e.g., the neighborhood node), or providing anoptimized drive path. Alternately the routing guidance may be directedto a technician engaged in some non-ingress related activity, but fromwhose vehicle ingress data may be passively collected, such that thetechnician might make relatively minor course deviations, relative totheir primary assignment, in order to map some nearby area of interest(e.g., a neighborhood node). This directed passive mapping may be inresponse to a gap in or undue age of the data covering a particularplant segment, or in response to some suspected problem/fault in thearea of interest that might benefit from more current data or a higherspatial resolution.

In yet other embodiments, low-frequency downstream egress may be used togather data that may assists in ingress detection. This data may beobtained, for example, by monitoring a signal in the network's forwardpath that is closer to the return path frequency range than is nowcustomary. The carrier present at E.I.A. channel 2 (i.e., the lowestfrequency in the forward lineup, and therefore closest to the returnbandwidth) may be utilized, or a narrow carrier injected at the head endinto the forward path below channel 2, but above the diplex filtercutoff (generally 50 MHz to 52 MHz), expressly for this purpose. Thisapproach avoids the requirement of two-way communication to get bothamplitude and position data, and may operate entirely passively.

A variation on the passive approaches detailed above that may beprovided in various implementations includes “listening” for return pathtraffic (i.e., DOCSIS subscriber modems) as egress from the cablecommunication system. This implementation may yield useful datapassively, and at precisely the frequencies of highest concern in thereturn path (i.e., where the DOCSIS carriers reside). The data gatheredin this way may also be tagged with a MAC address of the transmittingmodem, further information that may be used diagnostically.

In accordance with various aspects of some embodiments of the presentinvention, customer premise equipment (CPE) (i.e., subscriber premisesequipment) may be repurposed and implemented as an integral componentfor ingress detection. More specifically, a piece of CPE may temporarilybe controlled (for example, by command from the CMTS, during, forexample, idle cycles) to check for the presence (and relative amplitude)of the ingress test transmission and report the results back via theDOCSIS data stream. This data may assist in directly identifying aprospective ingress point entering the cable communication systembetween the tap and the reporting piece of CPE. Since the physicaladdress of each CPE is known, the fault occurs along the connection pathto the subscriber premise. Such an implementation may be completed as arapid system ride-out, without having to disconnect any subscriberservice drops or other connections during testing. It would only,however, be sensitive to ingress faults inline with the particularbranch of in-home wiring that feeds the CPE device in question.

VI. INVENTIVE CABLE COMMUNICATION SYSTEMS

With reference again to Section I above, to demonstrate the efficacy ofingress mitigation methods, apparatus and systems according to variousembodiments of the present invention, the phase 1 and phase 2 activitiesdescribed herein were performed in connection with a neighborhood nodeof an operational cable communication system (e.g., ingress mitigatednode BT-11). More specifically, three iterations of phase 1 and phase 2activity were performed over the period of about one week, with anadditional final iteration of phase 1 to ascertain the effectiveness ofthe final phase 2 activity (i.e., four iterations of phase 1, threeiterations of phase 2). Before ingress mitigation efforts, a noisespectrum for the upstream path bandwidth of the ingress mitigated nodeBT-11 was taken (e.g., 24 hour average noise power across the upstreampath bandwidth), and various metrics (e.g., C/N, MER) were observed fora test channel having a carrier frequency of 16.4 MHz (e.g., see FIG. 27and the test channel 2103T provided by the test modem 1065) (so as toobtain pre-mitigation data). For each iteration of phase 1, an ingressneighborhood node map in the form of a heat map was generated (e.g., seethe time series of heat maps 300A, 300B, 300C and 300D shown in FIGS.33-36). Following each iteration of phase 2, various measurements weretaken in connection with the upstream path bandwidth of the ingressmitigated node BT-11 and the test channel 2103T. Accordingly, a timeseries of heat maps, upstream path bandwidth spectra (illustrating thetest channel and any noise within the upstream path bandwidth), testchannel MER measurements (unequalized and equalized) and associatedconstellation diagrams were obtained, from which incremental reductionsin ingress and improvements in test channel metrics were unambiguouslyobserved. Additionally, pre-mitigation and post-mitigation comparisonsof all measurements revealed a dramatic reduction in ingress and overallimprovement in test channel metrics.

FIG. 50 illustrates a spectrum 2100D of the upstream path bandwidth ofthe ingress mitigated node BT-11 in which the test channel 2103T havinga carrier frequency of 16.4 MHz and a bandwidth 2109 of 3.2 MHz istransmitting, prior to ingress mitigation and corresponding to the heatmap of FIG. 33. The spectrum 2100D of FIG. 50 shows multiple significantingress disturbances 3500 present at frequencies from approximately 5MHz to approximately 15 MHz, and more particularly from approximately 10MHz to approximately 15 MHz. A noise floor 2107 of the spectrum 2100D atfrequencies of about 20 MHz and higher is about −52 dBmV, and theaverage channel power of the test channel 2103T is approximately −6dBmV. From FIG. 50, it may be observed that the peak of the highestpower ingress carrier (at about 13.5 MHz) is only approximately 16 dBlower than the average channel power. It is also noteworthy that it isimpossible to determine from the spectrum 2100D of FIG. 50 if there areone or more additional ingress carriers that fall within the bandwidth2109 of the test channel 2103T; in fact, from MER measurements of thetest channel corresponding to the spectrum 2100D (discussed furtherbelow in connection with FIG. 57), it may be reasonably presumed thatindeed there is a significant presence of ingress disturbances withinthe bandwidth 2109 of the test channel 2103T (leading to a notably lowCNIR for the test channel).

FIG. 51 illustrates a spectrum 2100E of the same upstream path bandwidthmonitored in FIG. 50, after a first iteration of ingress remediation andcorresponding to the heat map of FIG. 34. Although the spectrum 2100Estill reveals a significant presence of ingress disturbances 3500 belowapproximately 15 MHz, it may be observed that the a peak of the highestpower ingress carrier (at about 7 MHz) is lower as compared to thehighest power ingress carrier in the spectrum 2100D, and approximately22 dB lower than the average channel power of the test channel 2103T. Itis also noteworthy in FIG. 51 that additional ingress disturbances haveappeared in the spectrum 2100E above 20 MHz (e.g., see ingress carrierat approximately 27 MHz), providing evidence of the time-varying natureof some ingress disturbances.

FIG. 52 illustrates a spectrum 2100F of the same upstream path bandwidthmonitored in FIGS. 50 and 51, after a second iteration of ingressremediation and corresponding to the heat map of FIG. 35. Althoughingress disturbances 3500 are still present to some extent in thespectrum 2100F, there is a marked reduction in the power level of suchdisturbances. The noise floor 2107 in the vicinity of the test channel2103T is approximately −48 dBmV (and somewhat lower above 20 MHz) andthe average channel power of the test channel is approximately −6 dBmV,evidencing an apparent carrier-to-noise ratio (CNR) 2105 ofapproximately 42 dB. With reference again to Table 6, such a CNR issuitable for supporting a QAM channel having a modulation order of up to1024 (1024-QAM), without error correction, to achieve a bit error ratio(BER) on the order of 10⁻⁸. If FEC is employed, this CNR is sufficientto support QAM channels having a modulation order of up to 4096(4096-QAM).

FIG. 53 illustrates a spectrum 2100G of the same upstream path bandwidthmonitored in FIGS. 50, 51, and 52, after a third iteration of ingressremediation and corresponding to the heat map of FIG. 36. In FIG. 53, adramatic reduction and virtual eradication of the ingress disturbancesbelow approximately 15 MHz may be observed, with only a relatively minoringress carrier 3504 observable at approximately 9 MHz. In the spectrum2100G of FIG. 53, the noise floor 2107 in the vicinity of the testchannel 2103T, and throughout the spectrum from approximately 5 MHz toapproximately 20 MHz, is approximately −50 dBmV, and a difference 2111between the peak power level of the largest remaining ingress carrier3504 and the noise floor 2107 is approximately 6 dB; i.e., the noisefloor 2107 is remarkably flat from approximately 5 MHz to approximately20 MHz. Most significantly, in addition to an appreciably flat noisefloor 2107, the spectrum 2100G of FIG. 53 reveals a CNR 2105 for thetest channel 2103T of approximately 44 dB; with reference again to Table6, such a CNR is suitable for supporting a QAM channel having amodulation order of up to 2048 (2048-QAM), without error correction, toachieve a bit error ratio (BER) on the order of 10⁻⁸.

FIG. 54 illustrates a comparison of a first spectrum 2150A representinga 24 hour average noise power in the ingress mitigated node BT-11, priorto ingress mitigation according to the present invention, and a secondspectrum 2150B representing a 24 hour average noise power in the ingressmitigated node BT-11 following the iterative ingress mitigation processdescribed above. As with the spectrum 2100G shown in FIG. 53, thespectra shown in FIG. 54 reveal a dramatic and sustained reduction iningress across the entire upstream path bandwidth from approximately 5MHz to approximately 42 MHz. In particular, above approximately 20 MHz,sustained reduction in the noise floor of approximately 4 dB to 6 dB maybe observed; below approximately 20 MHz, significant reductions iningress may be observed, in which a difference 2113 between the highestingress peak prior to ingress mitigation (at approximately 6.5 MHz) andafter ingress mitigation is approximately 14 dB.

FIG. 55 illustrates a three-dimensional graph showing a first timeseries of hourly spectra of the upstream path bandwidth of the ingressmitigated node BT-11, prior to ingress mitigation according to thepresent invention, which served as the basis for the 24 hour averagenoise power measurements shown in the spectrum 2150A of FIG. 54. FromFIG. 55, the time-varying nature of ingress may be clearly observed.FIG. 56 illustrates a three-dimensional graph showing a second timeseries of hourly spectra of the upstream path bandwidth of the ingressmitigated node BT-11 over another 24 hour period, following ingressmitigation according to the present invention, which served as the basisfor the 24 hour average noise power measurements shown in the spectrum2150B of FIG. 54. Although noteworthy time variations in ingress stillcan be seen in FIG. 56 over the 24 hour period observed post-mitigation,there is nonetheless a dramatic reduction of ingress across the entireupstream path bandwidth and throughout the entire 24 hour periodobserved.

FIGS. 57 through 60 are graphs 2200A, 2200B, 2200C, and 2200Drespectively illustrating unequalized and equalized modulation errorratio (MER) of the test channel 2103T (shown in the correspondingspectra of FIGS. 50 through 53) as a function of packets received, aftereach iteration of ingress remediation discussed above. In the graph2200A of FIG. 57, both unequalized and equalized MER measurements aresignificantly erratic; with reference again to FIG. 50 and the spectrum2100D (during which the MER measurements shown in FIG. 57 were taken),such erratic MER strongly suggests the presence of one or more ingresscarriers within the bandwidth 2109 of the test channel 2103T. In thegraphs 2200B and 2200C shown in FIGS. 58 and 59, notable improvement inMER is seen with each iteration of ingress remediation, in whichunequalized MER is consistently greater than 25 dB (although somewhatless stable above approximately 26 to 27 dB). With reference again toTable 5, the MER measurements demonstrated in FIGS. 58 and 59nonetheless are sufficient to support a QAM channel having a modulationorder of at least 32 (32-QAM) and as high as 64 (64-QAM).

In the graph 2200D of FIG. 60, which corresponds to the spectrum 2100Gof FIG. 53, a significant improvement in the value and stability of bothunequalized and equalized MER for the test channel 2103T may beobserved; in particular a very stable unequalized MER of approximately30 dB is achieved, and a stable equalized MER of approximately 40 dB isachieved. With reference again to Table 5, these MER measurements aresufficient to support a QAM channel having a modulation order of atleast 64 (64-QAM) and as high as 256 (256-QAM) or even higher (e.g., ifLDPC error correction is employed). With reference again to the spectrum2100G of FIG. 53, and in view of the substantially flat noise floor 2107across the upstream path bandwidth (particularly below approximately 20MHz), the MER measurements provided in the graph 2200D of FIG. 60support placement of QAM channels having a modulation order of 64, andas high as at least 256, virtually anywhere within the upstream pathbandwidth

To provide another visually intuitive illustration of the efficacy ofingress mitigation methods, apparatus, and systems according to variousembodiments of the present invention in terms of channel performance,FIGS. 61A and 61B represent pre-ingress mitigation and post-ingressmitigation constellation diagrams, respectively, for the test channel2103T shown in FIGS. 50 through 53 (the constellation diagram of FIG.61A corresponds to the spectrum 2100D shown in FIG. 50, and theconstellation diagram of FIG. 61B corresponds to the spectrum 2100Gshown in FIG. 53). In terms of the spread or “fuzziness” of therespective symbol clouds in the constellation diagrams, significantlyless fuzzy and “tighter” symbol clusters may be readily observed in theconstellation diagram of FIG. 61B as a result of ingress mitigation.

In addition to using a QPSK test channel to observe reduced ingress andimproved performance on the ingress mitigated node BT-11, the ingressmitigated node BT-11 also was equipped, post-mitigation, with a testmodem and demodulation tuner supporting a 16-QAM ATDMA test channelhaving a carrier frequency of 16.4 MHz and a bandwidth of 3.2 MHz. FIG.62 shows a screen-shot of a QAM analyzer coupled to the headend of thecommunication system, illustrating a post-ingress mitigationconstellation diagram and graph of unequalized MER as a function ofpackets received, for the 16-QAM ATDMA test channel. From FIG. 62, itmay be readily observed that an unequalized MER of approximately 30 dBsimilarly is achieved for the 16-QAM ATDMA test channel, with tightsymbol clusters in the constellation diagram.

Similarly, four other “control nodes” of the cable communication systemin which ingress mitigation was not performed respectively were equippedwith test modems and demodulation tuners supporting a 16-QAM ATDMA testchannel having a carrier frequency of 16.4 MHz and a bandwidth of 3.2MHz. FIG. 63A shows the constellation diagram from the screen-shot ofFIG. 62, and FIGS. 63B, 63C, 63D and 63E show similar constellationdiagrams for 16-QAM ATMDA test channels used respectively in the fourother control nodes of the cable communication system. The constellationdiagrams of FIGS. 63B and 63C reveal significantly fuzzier clouds forthe constellation symbols than those shown in FIG. 64A corresponding tothe ingress mitigated node BT-11. In the control nodes represented bythe constellation diagrams shown in FIGS. 63D and 63DE, the test modemswould not even lock due at least in part to a significant presence ofingress.

Thus, pursuant to various inventive ingress mitigation methods andapparatus disclosed herein, improved cable communication systems andmethods according to other embodiments of the present invention may berealized that previously were not possible. In particular, existingcable communication systems may be modified (e.g., repaired and/orupdated with new components) pursuant to the ingress mitigation methodsand apparatus disclosed herein to yield significantly improved cablecommunication systems according to various embodiments of the presentinvention. Similarly, new cable communication systems according tovarious embodiments of the present invention may be deployed in which,as part of a quality assessment of the newly installed system forexample, the ingress mitigation methods and apparatus disclosed hereinmay be applied to ascertain that various noise metrics are met toaccommodate significant increases in aggregate deployed upstreamcapacity as compared to conventional cable communication systems, and togenerally ensure reliable operation of the newly installed system. Forboth pre-existing and newly installed cable communication systems,ingress mitigation methods and apparatus according to variousembodiments of the present invention may be employed as part of aperiodic (e.g., routine or occasional) cable communication systemmaintenance program to ensure ongoing reliability of such increasedupstream capacity systems.

Furthermore, the Inventors have recognized and appreciated that adramatic reduction of ingress in a given neighborhood node, particularlybelow approximately 20 MHz, also may provide for greater effectivenessof ingress cancellation circuitry employed in some cable modemtermination system (CMTS) demodulation tuners, and/or obviate the needin some instances for advanced access protocols such as Synchronous CodeDivision Multiple Access (S-CDMA), thereby permitting expanded use ofTDMA/ATDMA channels in a previously unusable portion of the upstreampath bandwidth. In particular, cable communication systems according tovarious embodiments of the present invention having significantlyreduced noise in the upstream path bandwidth of respective neighborhoodnodes enable an expanded use of commonly implemented TDMA/ATDMA channelsbelow 20 MHz to increase upstream capacity for supporting voice and/ordata services.

Moreover, such reduced noise cable communication systems enable theimplementation of upstream QAM channels with higher modulation orders(and hence increased deployed channel data rates) throughout theupstream path bandwidth from approximately 5 MHz to at leastapproximately 42 MHz as compared to conventional cable communicationsystems (even in the absence of forward error correction, adaptiveequalization and/or ingress cancellation), thus providing significantlyincreased aggregate deployed upstream capacity in a given neighborhoodnode. For example, with reference again to FIG. 26, by using QAMchannels having a modulation order as high as 256 throughout theupstream path bandwidth from approximately 5.2 MHz to approximately 42MHz in a given neighborhood node of a cable communication systemaccording to one embodiment of the present invention, a total aggregatedeployed upstream capacity of approximately 240 Mbits/s may berealized—almost doubling the aggregate deployed upstream capacity of“state-of-the-art” conventional cable communication systems.

When reduced noise cable communication systems according to variousembodiments of the present invention are coupled with one or more ofadaptive equalization and ingress cancellation for physicalcommunication channels, forward error correction (e.g., Reed-Solomon FECor LDPC—see Table 6 above), and optionally advanced protocols such asS-CDMA or Orthogonal Frequency Division Multiplexing (OFDM), evenfurther enhancements in aggregate deployed upstream capacity may berealized in the upstream path bandwidth of respective neighborhood nodesof the system (e.g., using QAM channels having modulation orders inexcess of 256). In particular, in other embodiments, cable communicationsystems may be realized in which the noise profile of a givenneighborhood node (e.g., the noise floor arising from AWGN, and otherdisturbances/interference combined therewith) over a substantial portionof the upstream path bandwidth from approximately 5 MHz to at leastapproximately 42 MHz allows for C/N values that, when combined withadvanced error correction techniques such as LDPC, support functioningQAM channels having modulation orders in excess of 256 (e.g., see Table6, in which a C/N value of 34 dB supports 4096-QAM using LDPC ⅚ errorcorrection). In this manner, aggregate deployed upstream capacities ofup to approximately 350 Mbits/s may be achieved in cable communicationsystems according to various embodiments of the present invention (e.g.,using 4096-QAM channels having a deployed data rate of 9.6 Mbits/s/MHzacross the upstream path bandwidth from approximately 5 MHz to at leastapproximately 42 MHz; see Table 3).

VII. CONCLUSION

While various inventive embodiments have been described and illustratedherein, those of ordinary skill in the art will readily envision avariety of other means and/or structures for performing the functionand/or obtaining the results and/or one or more of the advantagesdescribed herein, and each of such variations and/or modifications isdeemed to be within the scope of the inventive embodiments describedherein. More generally, those skilled in the art will readily appreciatethat all parameters, dimensions, materials, and configurations describedherein are meant to be exemplary and that the actual parameters,dimensions, materials, and/or configurations will depend upon thespecific application or applications for which the inventive teachingsis/are used. Those skilled in the art will recognize, or be able toascertain using no more than routine experimentation, many equivalentsto the specific inventive embodiments described herein. It is,therefore, to be understood that the foregoing embodiments are presentedby way of example only and that, within the scope of the appended claimsand equivalents thereto, inventive embodiments may be practicedotherwise than as specifically described and claimed. Inventiveembodiments of the present disclosure are directed to each individualfeature, system, article, material, kit, and/or method described herein.In addition, any combination of two or more such features, systems,articles, materials, kits, and/or methods, if such features, systems,articles, materials, kits, and/or methods are not mutually inconsistent,is included within the inventive scope of the present disclosure.

The above-described embodiments can be implemented in any of numerousways. For example, the embodiments may be implemented using hardware,software or a combination thereof. When implemented in software, thesoftware code can be executed on any suitable processor or collection ofprocessors, whether provided in a single computer or distributed amongmultiple computers.

Further, it should be appreciated that a computer may be embodied in anyof a number of forms, such as a rack-mounted computer, a desktopcomputer, a laptop computer, or a tablet computer. Additionally, acomputer may be embedded in a device not generally regarded as acomputer but with suitable processing capabilities, including a PersonalDigital Assistant (PDA), a smart phone or any other suitable portable orfixed electronic device.

Also, a computer may have one or more input and output devices. Thesedevices can be used, among other things, to present a user interface.Examples of output devices that can be used to provide a user interfaceinclude printers or display screens for visual presentation of outputand speakers or other sound generating devices for audible presentationof output. Examples of input devices that can be used for a userinterface include keyboards, and pointing devices, such as mice, touchpads, and digitizing tablets. As another example, a computer may receiveinput information through speech recognition or in other audible format.

Such computers may be interconnected by one or more networks in anysuitable form, including a local area network or a wide area network,such as an enterprise network, an intelligent network (IN) or theInternet. Such networks may be based on any suitable technology and mayoperate according to any suitable protocol and may include wirelessnetworks, wired networks or fiber optic networks.

Any computer discussed herein may comprise a memory, one or moreprocessing units (also referred to herein simply as “processors”), oneor more communication interfaces, one or more display units, and one ormore user input devices (user interfaces). The memory may comprise anycomputer-readable media, and may store computer instructions (alsoreferred to herein as “processor-executable instructions”) forimplementing the various functionalities described herein. Theprocessing unit(s) may be used to execute the instructions. Thecommunication interface(s) may be coupled to a wired or wirelessnetwork, bus, or other communication means and may therefore allow thecomputer to transmit communications to and/or receive communicationsfrom other devices. The display unit(s) may be provided, for example, toallow a user to view various information in connection with execution ofthe instructions. The user input device(s) may be provided, for example,to allow the user to make manual adjustments, make selections, enterdata or various other information, and/or interact in any of a varietyof manners with the processor during execution of the instructions.

The various methods or processes outlined herein may be coded assoftware that is executable on one or more processors that employ anyone of a variety of operating systems or platforms. Additionally, suchsoftware may be written using any of a number of suitable programminglanguages and/or programming or scripting tools, and also may becompiled as executable machine language code or intermediate code thatis executed on a framework or virtual machine.

In this respect, various inventive concepts may be embodied as acomputer readable storage medium (or multiple computer readable storagemedia) (e.g., a computer memory, one or more floppy discs, compactdiscs, optical discs, magnetic tapes, flash memories, circuitconfigurations in Field Programmable Gate Arrays or other semiconductordevices, or other non-transitory medium or tangible computer storagemedium) encoded with one or more programs that, when executed on one ormore computers or other processors, perform methods that implement thevarious embodiments of the invention discussed above. The computerreadable medium or media can be transportable, such that the program orprograms stored thereon can be loaded onto one or more differentcomputers or other processors to implement various aspects of thepresent invention as discussed above.

The terms “program” or “software” are used herein in a generic sense torefer to any type of computer code or set of computer-executableinstructions that can be employed to program a computer or otherprocessor to implement various aspects of embodiments as discussedabove. Additionally, it should be appreciated that according to oneaspect, one or more computer programs that when executed perform methodsof the present invention need not reside on a single computer orprocessor, but may be distributed in a modular fashion amongst a numberof different computers or processors to implement various aspects of thepresent invention.

Computer-executable instructions may be in many forms, such as programmodules, executed by one or more computers or other devices. Generally,program modules include routines, programs, objects, components, datastructures, etc. that perform particular tasks or implement particularabstract data types. Typically the functionality of the program modulesmay be combined or distributed as desired in various embodiments.

Also, data structures may be stored in computer-readable media in anysuitable form. For simplicity of illustration, data structures may beshown to have fields that are related through location in the datastructure. Such relationships may likewise be achieved by assigningstorage for the fields with locations in a computer-readable medium thatconvey relationship between the fields. However, any suitable mechanismmay be used to establish a relationship between information in fields ofa data structure, including through the use of pointers, tags or othermechanisms that establish relationship between data elements.

Various embodiments described herein are to be understood in both openand closed terms. In particular, additional features that are notexpressly recited for an embodiment may fall within the scope of acorresponding claim, or can be expressly disclaimed (e.g., excluded bynegative claim language), depending on the specific language recited ina given claim.

Unless otherwise stated, any first range explicitly specified also mayinclude or refer to one or more smaller inclusive second ranges, eachsecond range having a variety of possible endpoints that fall within thefirst range. For example, if a first range of 3 dB<x<10 dB is specified,this also specifies, at least by inference, 4 dB<x<9 dB, 4.2 dB<x<8.7dB, and the like.

Also, various inventive concepts may be embodied as one or more methods,of which an example has been provided. The acts performed as part of themethod may be ordered in any suitable way. Accordingly, embodiments maybe constructed in which acts are performed in an order different thanillustrated, which may include performing some acts simultaneously, eventhough shown as sequential acts in illustrative embodiments.

All definitions, as defined and used herein, should be understood tocontrol over dictionary definitions, definitions in documentsincorporated by reference, and/or ordinary meanings of the definedterms.

The indefinite articles “a” and “an,” as used herein in thespecification and in the claims, unless clearly indicated to thecontrary, should be understood to mean “at least one.”

The phrase “and/or,” as used herein in the specification and in theclaims, should be understood to mean “either or both” of the elements soconjoined, i.e., elements that are conjunctively present in some casesand disjunctively present in other cases. Multiple elements listed with“and/or” should be construed in the same fashion, i.e., “one or more” ofthe elements so conjoined. Other elements may optionally be presentother than the elements specifically identified by the “and/or” clause,whether related or unrelated to those elements specifically identified.Thus, as a non-limiting example, a reference to “A and/or B”, when usedin conjunction with open-ended language such as “comprising” can refer,in one embodiment, to A only (optionally including elements other thanB); in another embodiment, to B only (optionally including elementsother than A); in yet another embodiment, to both A and B (optionallyincluding other elements); etc.

As used herein in the specification and in the claims, “or” should beunderstood to have the same meaning as “and/or” as defined above. Forexample, when separating items in a list, “or” or “and/or” shall beinterpreted as being inclusive, i.e., the inclusion of at least one, butalso including more than one, of a number or list of elements, and,optionally, additional unlisted items. Only terms clearly indicated tothe contrary, such as “only one of” or “exactly one of,” or, when usedin the claims, “consisting of,” will refer to the inclusion of exactlyone element of a number or list of elements. In general, the term “or”as used herein shall only be interpreted as indicating exclusivealternatives (i.e. “one or the other but not both”) when preceded byterms of exclusivity, such as “either,” “one of,” “only one of,” or“exactly one of” “Consisting essentially of,” when used in the claims,shall have its ordinary meaning as used in the field of patent law.

As used herein in the specification and in the claims, the phrase “atleast one,” in reference to a list of one or more elements, should beunderstood to mean at least one element selected from any one or more ofthe elements in the list of elements, but not necessarily including atleast one of each and every element specifically listed within the listof elements and not excluding any combinations of elements in the listof elements. This definition also allows that elements may optionally bepresent other than the elements specifically identified within the listof elements to which the phrase “at least one” refers, whether relatedor unrelated to those elements specifically identified. Thus, as anon-limiting example, “at least one of A and B” (or, equivalently, “atleast one of A or B,” or, equivalently “at least one of A and/or B”) canrefer, in one embodiment, to at least one, optionally including morethan one, A, with no B present (and optionally including elements otherthan B); in another embodiment, to at least one, optionally includingmore than one, B, with no A present (and optionally including elementsother than A); in yet another embodiment, to at least one, optionallyincluding more than one, A, and at least one, optionally including morethan one, B (and optionally including other elements); etc.

In the claims, as well as in the specification above, all transitionalphrases such as “comprising,” “including,” “carrying,” “having,”“containing,” “involving,” “holding,” “composed of,” and the like are tobe understood to be open-ended, i.e., to mean including but not limitedto. Only the transitional phrases “consisting of” and “consistingessentially of” shall be closed or semi-closed transitional phrases,respectively, as set forth in the United States Patent Office Manual ofPatent Examining Procedures, Section 2111.03.

1-48. (canceled)
 49. A method for facilitating detection of ingress in at least one neighborhood node of a cable communication system, the cable communication system comprising: a headend or hub comprising: a headend optical/radio frequency (RF) converter; and a cable modem system coupled to the headend optical/RF converter; and a first neighborhood node of the at least one neighborhood node, the first neighborhood node having an infrastructure comprising: a first fiber optic cable coupled to the headend optical/RF converter; a first node optical/RF converter coupled to the first fiber optic cable; a first RF hardline coaxial cable plant, coupled to the first node optical/RF converter and traversing the first neighborhood node, to convey to the headend or hub at least first upstream information from a plurality of first subscriber premises over an upstream path bandwidth including a range of frequencies from approximately 5 MHz to at least approximately 42 MHz; and a plurality of first subscriber service drops, coupled to the first RF hardline coaxial cable plant and to the plurality of first subscriber premises, to provide the first upstream information from the plurality of first subscriber premises to the first RF hardline coaxial cable plant, the method comprising: A) directing a mobile broadcast apparatus including a transmitter along a first neighborhood node drive path proximate to the first RF hardline coaxial cable plant so as to effectively traverse and ensure substantially full coverage of the first subscriber neighborhood; B) during A), broadcasting from the transmitter a test signal at a plurality of locations distributed along at least a substantial portion of the first neighborhood node drive path, the test signal having at least one test signal frequency falling within the upstream path bandwidth; C) during A), electronically recording first geographic information corresponding to respective positions of the mobile broadcast apparatus along at least the substantial portion of the first neighborhood node drive path so as to generate a first record of the first geographic information; D) during A) and throughout traversing at least the substantial portion of the first neighborhood node drive path, recording, via an analyzer coupled to a first junction of the cable modem system and the headend optical/RF converter or a second junction of the hardline cable plant and the first node optical/RF converter, a plurality of signal amplitudes at the test signal frequency so as to generate a second record, the plurality of signal amplitudes representing a strength of a received upstream test signal as a function of time, based on B) and test signal ingress of the test signal into at least one fault in the first RF hardline coaxial cable plant; and E) based on the first record generated in C) and the second record generated in D), electronically generating a first neighborhood node ingress map comprising: a first graphical representation of the first neighborhood node drive path; and a second graphical representation, overlaid on the first graphical representation, of the plurality of signal amplitudes, at least along the substantial portion of the first neighborhood node drive path, so as to illustrate the test signal ingress of the test signal into at least the first RF hardline coaxial cable plant of the first neighborhood node.
 50. The method of claim 49, wherein: B) comprises broadcasting from the transmitter the test signal at the plurality of locations distributed along an entirety of the first neighborhood node drive path; C) comprises electronically recording the first geographic information corresponding to the respective positions of the mobile broadcast apparatus along the entirety of the first neighborhood node drive path so as to generate the first record of the first geographic information; D) comprises recording the plurality of signal amplitudes at the test signal frequency throughout traversing the entirety of the first neighborhood node drive path so as to generate the second record; and in E), the second graphical representation is based on the plurality of signal amplitudes recorded along the entirety of the first neighborhood node drive path, so as to illustrate the test signal ingress of the test signal into at least the first RF hardline coaxial cable plant of the first neighborhood node.
 51. The method of claim 49, wherein in B), the test signal does not include the geographic information for the plurality of locations recorded in C).
 52. The method of claim 49, wherein B) comprises: B1) modulating the test signal so as to mitigate significant interference in the upstream path bandwidth with the first upstream information from the plurality of first subscriber premises.
 53. The method of claim 52, wherein B1) comprises spread spectrum modulating the test signal.
 54. The method of claim 52, wherein B1) comprises time division multiplexing the test signal.
 55. The method of claim 54, wherein: the upstream path bandwidth includes a plurality of time slots; the plurality of time slots include a plurality of subscriber premises time slots and at least one dedicated time slot for the test signal; the plurality of subscriber premises are assigned respective subscriber premises time slots of the plurality of subscriber premises time slots to transmit at least some of the first upstream information in the upstream path bandwidth; and B1) comprises broadcasting the test signal during the dedicated time slot.
 56. The method of claim 49, wherein B1) comprises: broadcasting the test signal as at least one pulsed test signal.
 57. The method of claim 56, wherein a duration of one or more pulses of the at least one pulsed test signal is less than a symbol length of the first upstream information from the plurality of first subscriber premises.
 58. The method of claim 49, wherein B) comprises: during A), broadcasting from the transmitter the test signal at a sufficiently low power as transmitted by the transmitter so as not to require licensure from one or more regulatory authorities.
 59. The method of claim 49, wherein B) comprises: during A), broadcasting from the transmitter the test signal at at least one test signal frequency between 5 MHz and 16 MHz.
 60. The method of claim 49, wherein B) comprises: during A), varying the at least one test signal frequency, as a function of time, across at least a portion of the upstream path bandwidth.
 61. The method of claim 49, wherein: the at least one test signal frequency includes a plurality of test signal frequencies; and B) further comprises: B1) broadcasting, during A), the test signal at the plurality of test signal frequencies.
 62. The method of claim 61, wherein B1) comprises broadcasting the test signal at at least two of the plurality of test signal frequencies simultaneously.
 63. The method of claim 61, wherein the test signal includes a spread spectrum test signal.
 64. The method of claim 49, wherein B) comprises: B1) broadcasting the test signal during operative signaling in the upstream path bandwidth from at least some of the plurality of first subscriber premises, wherein the at least one test signal frequency falls within a frequency range of the operative signaling in the upstream path bandwidth.
 65. The method of claim 64, wherein B1) further comprises: varying the at least one test signal frequency, as a function of time, across a substantial portion of the frequency range of the operative signaling in the upstream path bandwidth.
 66. The method of claim 49, wherein: C) comprises: during A), electronically recording the first geographic information corresponding to the respective positions of the mobile broadcast apparatus along at least the substantial portion of the first neighborhood node drive path as a first ordered sequence of points so as to generate the first record of the first geographic information as a function of time; and D) comprises: during A) and throughout traversing at least the substantial portion of the first neighborhood node drive path, recording, via the analyzer coupled to the first junction of the cable modem system and the headend optical/RF converter or the second junction of the hardline cable plant and the first node optical/RF converter, the plurality of signal amplitudes at the test signal frequency as a second ordered sequence of points so as to generate the second record, the plurality of signal amplitudes representing the strength of the received upstream test signal as a function of time, based on B) and the test signal ingress of the test signal into the at least one fault in the first RF hardline coaxial cable plant.
 67. The method of claim 66, wherein in D), the second ordered sequence of points is indexed to the first ordered sequence of points from C).
 68. The method of claim 66, wherein in C) and D), the first ordered sequence of points and the second ordered sequence of points respectively are sampled at a same time.
 69. The method of claim 49, wherein: C) comprises: during A), electronically recording the first geographic information corresponding to the respective positions of the mobile broadcast apparatus along at least the substantial portion of the first neighborhood node drive path, together with a plurality of first corresponding time stamps, so as to generate the first record of the first geographic information as a function of time; and D) comprises: during A) and throughout traversing at least the substantial portion of the first neighborhood node drive path, recording, via the analyzer coupled to the first junction of the cable modem system and the headend optical/RF converter or the second junction of the hardline cable plant and the first node optical/RF converter, the plurality of signal amplitudes at the test signal frequency together with a plurality of second corresponding time stamps so as to generate the second record, the plurality of signal amplitudes representing the strength of the received upstream test signal as a function of time, based on B) and the test signal ingress of the test signal into the at least one fault in the first RF hardline coaxial cable plant.
 70. The method of claim 69, wherein: at least a first portion of the first neighborhood node drive path includes a first-pass segment and a second-pass segment; based on the first geographic information and plurality of first corresponding time stamps recorded during C), the mobile broadcast apparatus has at least one substantially identical position along the first-pass segment and the second-pass segment, respectively, at different ones of the first corresponding time stamps; the second record includes respective signal amplitudes representing the strength of the received upstream test signal at different ones of the second corresponding time stamps substantially corresponding to the different ones of the first corresponding time stamps representing the at least one substantially identical position of the mobile broadcast apparatus along the first-pass segment and the second-pass segment; the method further comprises: F) electronically processing the respective signal amplitudes in the second record to provide an electronically-processed signal amplitude at the at least one substantially identical position along the first-pass segment and the second-pass segment; and in E), the second representation is based at least in part on the electronically-processed signal amplitude from F).
 71. The method of claim 70, wherein: F) comprises determining an average value of the respective signal amplitudes in the second record to provide an averaged signal amplitude at the at least one substantially identical position along the first-pass segment and the second-pass segment; and in E), the second representation is based at least in part on the averaged signal amplitude from F).
 72. The method of claim 70, wherein: F) comprises determining a difference value between the respective signal amplitudes in the second record to provide a differential signal amplitude at the at least one substantially identical position along the first-pass segment and the second-pass segment; and in E), the second representation is based at least in part on the differential signal amplitude from F).
 73. The method of claim 69, wherein E) comprises: E1) merging the first record and the second record, based at least in part on the plurality of first corresponding time stamps and the plurality of second corresponding time stamps, so as to generate a third record including at least the first geographic information corresponding to respective positions of the mobile broadcast apparatus and the plurality of signal amplitudes representing the strength of the received upstream test signal as a function of time; and E2) generating the first neighborhood node ingress map based at least in part on the third record.
 74. The method of claim 73, wherein: E1) comprises: adding to the third record second geographic information relating to additional locations in the first neighborhood node beyond the first neighborhood node drive path so as to generate an expanded third record; and interpolating the plurality of signal amplitudes representing the strength of the received upstream test signal as a function of time so as to include in the expanded third record estimated signal amplitudes corresponding to the additional locations; and E2) comprises generating the first neighborhood node ingress map based at least in part on the expanded third record.
 75. The method of claim 49, wherein in E), the second graphical representation of the plurality of signal amplitudes includes a visual code for at least the plurality of signal amplitudes.
 76. The method of claim 75, wherein the second graphical representation comprises a heat map representing the plurality of signal amplitudes.
 77. The method of claim 75, wherein the second graphical representation comprises a contour map representing the plurality of signal amplitudes.
 78. The method of claim 75, wherein: the visual code comprises a color code including a plurality of colors; and respective colors of the plurality of colors represent different signal amplitudes of the plurality of signal amplitudes.
 79. The method of claim 75, wherein: the visual code comprises a gray-tone scale including a plurality of shades of gray; and respective shades of gray of the plurality of shades of gray represent different signal amplitudes of the plurality of signal amplitudes.
 80. The method of claim 75, wherein the visual code includes at least one of: a plurality of different hatching styles, wherein respective hatching styles of the plurality of different hatching styles represent different signal amplitudes of the plurality of signal amplitudes; a plurality of different shading styles, wherein respective shading styles of the plurality of different shading styles represent different signal amplitudes of the plurality of signal amplitudes; and a plurality of different symbols, wherein respective symbols of the plurality of different symbols represent different signal amplitudes of the plurality of signal amplitudes.
 81. The method of claim 49, wherein in E): the first neighborhood node ingress map comprises a graph having a first axis and a second axis; the first graphical representation of the first neighborhood node drive path corresponds to the first axis, wherein a first scale of the first axis represents a distance or a time along the first neighborhood node drive path; a second scale of the second axis represents respective signal amplitude values of the plurality of signal amplitudes; and the second graphical representation of the plurality of signal amplitudes comprises a plot on the graph of the plurality of signal amplitudes as a function of the distance or the time along the first neighborhood node drive path.
 82. The method of claim 49, wherein E) comprises generating the first neighborhood node ingress map as a three-dimensional map having three coordinate axes, and wherein: the first graphical representation of the first neighborhood node drive path is rendered in a first plane of the three-dimensional map, wherein latitude and longitude coordinates for the first geographic information corresponding to the respective positions of the mobile broadcast apparatus are plotted along a first axis and a second axis, respectively, of the three coordinate axes; and the second graphical representation includes a graph of respective values of the plurality of signal amplitudes, wherein the respective values of the plurality of signal amplitudes are plotted along a third axis of the three coordinate axes.
 83. The method of claim 82, wherein the second graphical representation further includes a two-dimensional representation in the first plane of the three-dimensional map, the two-dimensional representation including a visual code for at least the plurality of signal amplitudes rendered.
 84. The method of claim 49, wherein: in A), the mobile broadcast apparatus is further equipped with an antenna and a receiver configured to measure ambient ingress; C) further comprises: during A), electronically recording, in tandem with the first geographic information, ambient ingress information corresponding to a strength of the ambient ingress as measured by the receiver along at least the substantial portion of the first neighborhood node drive path; and E) comprises generating the first neighborhood node ingress map to further include a third graphical representation, overlaid on the first and second graphical representations, of the ambient ingress information.
 85. The method of claim 49, wherein E) further comprises generating the first neighborhood node ingress map to further include: a third graphical representation, overlaid on the first and second graphical representations, of a cable facilities map showing at least a portion of the infrastructure of the first neighborhood node.
 86. The method of claim 49, wherein E) further comprises generating the first neighborhood node ingress map to further include: a third graphical representation, overlaid on the first and second graphical representations, of subscriber information showing respective locations of the plurality of first subscriber premises.
 87. The method of claim 86, wherein the third graphical representation includes at least one of a tax map and a parcel map.
 88. The method of claim 86, wherein the third graphical representation includes at least one of: at least one first indicator to indicate respective ones of the plurality of first subscriber premises; at least one second indicator to indicate one or more types of cable communication system services provided to the respective ones of the plurality of first subscriber premises; at least one third indicator to indicate a special status of at least one first subscriber premises of the plurality of first subscriber premises; and at least one fourth indicator to indicate respective ones of non-subscriber premises in the first neighborhood node.
 89. The method of claim 49, wherein E) further comprises generating the first neighborhood node ingress map to further include: a third graphical representation, overlaid on the first and second graphical representations, of at least one of an aerial image and a street map.
 90. The method of claim 49, wherein E) comprises generating the first neighborhood node ingress map as an electronic visual rendering having a plurality of independently selectable and independently viewable layers comprising at least two of: a first layer corresponding to the first graphical representation of the first neighborhood node drive path; a second layer corresponding to the second graphical representation of the plurality of signal amplitudes; a third layer corresponding to a third graphical representation of a cable facilities map showing at least a portion of the infrastructure of the first neighborhood node; a fourth layer corresponding to a fourth representation of subscriber information showing respective locations of the plurality of first subscriber premises; a fifth layer corresponding to a fifth graphical representation of at least one of an aerial image and a street map; and a sixth layer corresponding to a sixth representation of ambient ingress information in the first neighborhood node.
 91. The method of claim 49, further comprising: F) during A), electronically communicating to the mobile broadcast apparatus the plurality of signal amplitudes recorded in D) in substantially real time; and G) providing to a technician directing the mobile broadcast apparatus at least one audible indicator and/or at least one visual indicator based on the plurality of signal amplitudes, wherein at least one aspect of the at least one audible indicator and/or the at least one visual indicator is based at least in part on the strength of the received upstream test signal as a function of time.
 92. The method of claim 49, further comprising: F) electronically processing the plurality of signal amplitudes so as to automatically determine at least one potential point of first neighborhood node ingress due to the at least one fault in the first RF hardline coaxial cable plant of the first neighborhood node.
 93. The method of claim 92, wherein E) comprises: based on the first record in C), the second record generated in D), and the at least one potential point of first neighborhood node ingress determined in F), generating the first neighborhood node ingress map comprising: the first graphical representation of the first neighborhood node drive path; the second graphical representation, overlaid on the first graphical representation, of the plurality of signal amplitudes; and a third graphical representation, overlaid on the first graphical representation and the second graphical representation, of the at least one potential point of first neighborhood node ingress.
 94. The method of claim 92, wherein F) further comprises processing the plurality of signal amplitudes so as to automatically determine: a plurality of potential points of first neighborhood node ingress; and a relative severity of the plurality of potential points of first neighborhood node ingress so as to prioritize prospective repair or remediation activities in the first neighborhood node.
 95. The method of claim 94, wherein E) further comprises: based on the first record in C), the second record generated in D), and the plurality of potential points of first neighborhood node ingress and the relative severity determined in F), generating the first neighborhood node ingress map comprising: the first graphical representation of the first neighborhood node drive path; the second graphical representation, overlaid on the first graphical representation, of the plurality of signal amplitudes; and a third graphical representation, overlaid on the first graphical representation and the second graphical representation, of the relative severity of the plurality of potential points of first neighborhood node ingress.
 96. The method of claim 94, wherein: in A), the mobile broadcast apparatus is further equipped with an antenna and a receiver configured to measure ambient ingress; C) further comprises: during A), electronically recording, in tandem with the first geographic information, ambient ingress information corresponding to a strength of the ambient ingress as measured by the receiver along at least the substantial portion of the first neighborhood node drive path; and F) further comprises processing the plurality of signal amplitudes and the ambient ingress information so as to automatically determine the plurality of potential points of first neighborhood node ingress and the relative severity of the plurality of potential points of first neighborhood node ingress so as to prioritize the prospective repair or remediation activities in the first neighborhood node.
 97. The method of claim 94, wherein the plurality of potential points of first neighborhood node ingress comprises: at least one hardline plant-related point corresponding to the at least one hardline plant-related fault in the first RF hardline coaxial cable plant; and at least one subscriber-related point corresponding to at least one subscriber-related fault in at least one of the plurality of first subscriber service drops or at least one of the plurality of first subscriber premises.
 98. The method of claim 97, wherein F) further comprises processing the plurality of signal amplitudes and subscriber information so as to automatically determine the relative severity of the plurality of potential points of first neighborhood node ingress so as to prioritize the prospective repair or remediation activities in the first neighborhood node.
 99. The method of claim 98, wherein the subscriber information includes at least one of: one or more types of cable communication system services provided to the at least one of the plurality of first subscriber premises; and a special status of the at least one of the plurality of first subscriber premises.
 100. The method of claim 97, wherein E) further comprises: based on the first record in C), the second record generated in D), and the plurality of potential points of first neighborhood node ingress and the relative severity determined in F), generating the first neighborhood node ingress map comprising: the first graphical representation of the first neighborhood node drive path; the second graphical representation, overlaid on the first graphical representation, of the plurality of signal amplitudes; and a third graphical representation, overlaid on the first graphical representation and the second graphical representation, of the plurality of potential points of first neighborhood node ingress, wherein the third graphical representation includes different visual codes for the at least one subscriber-related point and the at least one hardline plant-related point, respectively.
 101. An apparatus for facilitating detection of ingress in at least a first neighborhood node of a cable communication system, the apparatus comprising: a communication interface; a display device; a memory to store processor-executable instructions; an analyzer; and a processor coupled to the communication interface, the display device, the analyzer, and the memory, wherein upon execution of the processor-executable instructions by the processor, the processor: A) controls the communication interface so as to receive a first record of first geographic information as a function of time, the first geographic information corresponding to respective positions of a mobile broadcast apparatus as directed along at least a substantial portion of a first neighborhood node drive path proximate to a first RF hardline coaxial cable plant in the first neighborhood node of the cable communication system; and B) controls the analyzer to measure a plurality of signal amplitudes representing a strength, at a headend or the first RF hardline coaxial cable plant of the cable communication system, of a received upstream test signal as a function of time, the strength of the received upstream test signal being based on: 1) a test signal broadcast from a transmitter in the mobile broadcast apparatus as the mobile broadcast apparatus is directed along the first neighborhood node drive path proximate to the first RF hardline coaxial cable plant; and 2) test signal ingress of the test signal into at least one fault in the RF hardline coaxial cable plant; C) generates a second record including the plurality of signal amplitudes measured in A2); D) controls the memory so as to store in the memory the first record and the second record; E) based on the first record and the second record, electronically generates a first neighborhood node ingress map comprising: E1) a first graphical representation of the first neighborhood node drive path; and E2) a second graphical representation, overlaid on the first graphical representation, of the plurality of signal amplitudes, at least along the substantial portion of the first neighborhood node drive path, so as to illustrate the test signal ingress of the test signal into at least the first RF hardline coaxial cable plant of the first neighborhood node; and F) controls the display device so as to display the first neighborhood node ingress map.
 102. A computer readable storage medium storing processor-executable instructions that, when executed by at least one processor, perform a method for facilitating detection of ingress in at least a first neighborhood node of a cable communication system, the method comprising: A) electronically receiving: A1) first geographic information as a function of time, the first geographic information corresponding to respective positions of a mobile broadcast apparatus as directed along at least a substantial portion of a first neighborhood node drive path proximate to a first RF hardline coaxial cable plant in the first neighborhood node of the cable communication system; and A2) a plurality of signal amplitudes representing a strength, as measured at a headend or the first RF hardline coaxial cable plant of the cable communication system, of a received upstream test signal as a function of time, the strength of the received upstream test signal being based on: 1) a test signal broadcast from a transmitter in the mobile broadcast apparatus as the mobile broadcast apparatus is directed along the first neighborhood node drive path proximate to the first RF hardline coaxial cable plant; and 2) test signal ingress of the test signal into at least one fault in the RF hardline coaxial cable plant; B) electronically processing the first geographic information to generate a first record based at least in part on the processed first geographic information; C) electronically processing the plurality of signal amplitudes to generate a second record based at least in part on the processed plurality of signal amplitudes; and D) based on the first record and the second record, electronically generating a first neighborhood node ingress map comprising: D1) a first graphical representation of the first neighborhood node drive path; and D2) a second graphical representation, overlaid on the first graphical representation, of the plurality of signal amplitudes, at least along the substantial portion of the first neighborhood node drive path, so as to illustrate the test signal ingress of the test signal into at least the first RF hardline coaxial cable plant of the first neighborhood node. 103-353. (canceled) 